I spent several months working in Oslo. The facts and comments here are not all applicable to other parts of Norway.
Norway is the most English-friendly (friendly to the English, and speaking English) place that I have ever been. Norway has a long history of connections with Britain (Queen Maud; and an abiding gratitude for the liberation from the Nazi invaders, hence the yearly gift of a giant Christmas tree put up in Trafalgar square). You really don't need to learn Norwegian to get by there: the only times that Norwegian is useful is to read signs and understand announcements on the trains.
I always felt welcome, and was never excluded from conversations between locals.
Oslo is also a safe city: the level of crime and violence is very low.
I was requested to add that many of the Norwegian women are beautiful: tall, slim and blond, but mostly not very tanned.
There is a Norwegian traditional style of clothing, similar to the Bavarian Trachtenmode. Locals tend to dress up in these outfits for national holidays and events such as Constitution Day (the Norwegians are very proud of their independence, and celebrate it on Constitution Day). People in Oslo do not celebrate mid-summer quite as seriously as the Swedes, although many people do barbecue either on their balconies or at parks (meat and sausages, usually, rather than the crayfish traditional in Sweden).
Don't underestimate the cost of living in Norway. It is the most expensive place I have ever lived; not somewhere to go for vacation on a tight budget. Salaries are high, as are social/government benefits, but they need to be because:
Some of the accommodation in Oslo is of a high standard, like Germany, but not all. I stayed in a flat in a new building, and it was well equipped, but far from perfect. You may need to shop around to find something that suits you.
Flats are expensive. My furnished flat was at Majorstuen, away from the centre; it was about a third of the size of my unfurnished apartment in Munich (the most expensive city in Germany), but it cost about 20% more.
There are a good selection of hotels in Oslo, to suit most budgets. I stayed at a Radisson Blu hotel, which is comfortable, for about 5 months, because my employer had a corporate deal, making it a reasonable price. I recommend checking the location of any hotel on a map before booking, as several are actually a long way out of town (for example, there are about 5 Radisson Blu hotels, and two of them are half an hour or more travel from the city centre).
Public transport is excellent in Oslo: there are tube trains (T-Ban), trams, and buses which all run frequently, and are clean and comfortable. Many shops (7-11, and Narvesen, for example) sell travel cards (electronic tickets which can be topped up).
There is a special high-speed train between Oslo Central Station and the airport (very comfortable), but even the normal train is pretty fast and perfectly fine for a short trip.
As in many countries, there are occasional ticket checks, and travelling without a ticket can result in an on-the-spot fine, although the ticket inspectors seem to be more reasonable than in some countries, if you have a sensible excuse.
The standard of roads in Norway is similar to Austria. There are only a limited number of motorway/autobahn-standard roads (e.g. between Oslo and Sweden); the rest are A-road or lower standard. Speed limits are therefore low, and if you drive, it may take you longer than you expect.
Norway has quite a lot of snow in winter, but the roads are generally kept clear. Even so, if you are not used to driving on snow, you should be careful.
You can get by perfectly in Norway with English. I also found that reading Norwegian was not so hard, as it has a lot of words in common with German, although understanding spoken Norwegian is another matter.
You will notice that there are a lot of words ending in "et". This is the definite article ("the") joined on to the end of the noun, as in "vinmonopolet" (the wine monopoly [shop]), in the same way as in Swedish.
Oslo has excellent medical infrastructure. Several of my colleagues had cause to go for medical treatment, and even for operations. They seemed to have little trouble finding such treatment, and seemed happy with the quality of service, although, again, it is expensive (both treatment and medicines).
I found some excellent restaurants in Oslo. Some of my favourites include the Brasserie France (expensive, but really excellent), the Ruffino (fantastic food and service, rightly rated as one of the best in Oslo), the Gate of India (the best Indian food that I had eaten in a restaurant in a long time), the Ophelia (a small menu, but well prepared, and some excellent wines), the Café Christiana (very popular with my Belgian colleagues), and the Olivia in Majorstuen (this is a chain, and not all their restaurants are up to the same standard).
Dining out is expensive in Oslo. Typically, expect to pay for one person, the same as you would pay for two in most of continental Europe.
Scandinavians have a reputation for loving seafood, but I was rather disappointed with the seafood restaurants. There are limited choices, and they are exorbitantly expensive. My girlfriend loves crab, and it was hard to find, and cost an arm and a leg.
I did notice some significant differences between food in Norway, and what I experienced in Sweden. The Swedes serve a lot of meat dishes with Lingon Berries (similar to cranberries); whilst I did have them (with Reindeer burgers at "Lorry") in Norway, they are much less common than in Sweden. The other difference that I noted was less beetroot; in Sweden beetroot is an ingredient of many sandwiches and salads (I am not a fan of beetroot, so I was very happy to see it on my plate less often in Norway).
Grocery shopping is not bad in Oslo, apart from the price. A colleague introduced me to an amazing Turkish shop, at Grønland, with a good selection of fruit, vegetables and other grocery items. There are also a selection of "supermarkets"; generally small, and with a selection limited by their size, but with good opening hours (but not Sundays, although that is under discussion). In Majorstuen there is also the Fromagerie, with an excellent selection of interesting imported (from France, Italy, Britain, etc.) cheeses, but it is expensive.
I had a lot of trouble finding sun-dried tomatoes, which I eventually managed to buy at the Fromagerie. I also never really found good sausages in Oslo. and took to bringing sausages with me from Germany.
If you spend any significant amount of time working in Norway, you are expected to register with the government. This means that you will be expected to pay local taxes. There is, however, no enforcement, and no requirement for employers to notify the government of foreigners working for them. Some people register, and some don't.
My experience was that the Norwegian police are polite and non-intrusive. One night, someone fell from the 4th-floor balcony of my apartment building in the middle of the night; the police rang my doorbell once, and then gave up (after having woken me, of course); they never questioned me.
There seem to be none of the ridiculous laws that we have in Germany (such as it being illegal to cross the road when the pedestrian crossing light is red, or doing laundry on a Sunday in certain areas).
I don't know how the TV licensing system works in Norway, nor what it costs, as that was included in my rent. Most apartments have cable TV, and there are a number of international channels. There are also international movies in original language (with Norwegian subtitles) on the Norwegian channels.
Oslo has excellent telecoms infrastructure. There are a range of operators, so competition is high, meaning prices are relatively cheap; the only thing that is, in Norway.
Also, as roaming charges are gradually phased out across Europe, it is becoming less expensive to use a non-Norwegian SIM cards there, and at least one UK operator already allows you to make and receive calls when in Norway at no extra charge.
Almost all restaurants, bars cafés and shopping malls have free WiFi, so it is possible to stay connected without incurring any charges.
Norwegians are very environmentally responsible (or at least they believe that they are).
Almost all bottles, both glass and plastic, and drinks cans, have a refundable deposit ("Pant"), although the deposits are small. You can recycle them, and get your deposit back, at any supermarket, and most other shops: there are machines into which you insert the bottle; the machines read the bar code, and give out a voucher which you can redeem at the checkout. Unlike most other countries, you can recycle any bottle or can at any store; you don't have to recycle items at the store where you bought them.
On the other hand, the facilities for recycling other valuable recyclable garbage are either non-existent, or cleverly disguised. I am used to separating metal, plastic, paper and glass, but the apartments have bins only for normal refuse and for paper/cardboard.
Cars, and other motor vehicles, are incredibly expensive in Norway, due to government duty. Electric vehicles, however, and completely free of such tax, making them good value, and this is why you will see so many Teslas on the road, as well as electric versions of may well-known brands of car. At the time of writing, electric cars are also allowed to drive in the bus/taxi lanes, and to park for free in the city, although this may change soon.
Norway, like Sweden and Finland, has a history of problems with alcoholism. As a result, you cannot buy anything stronger than beer except at the government alcohol shops (vinmonopolet), and it is expensive, due to the tax/duty. These shops also have restricted opening hours, meaning that, if you want to buy wine, you probably need to leave work early, or get up on Saturday at a reasonable time.
I also found the selection of wines rather odd. There were many varieties of some kinds of wines (those popular or well known in Norway), and in some cases a complete absence of other types of wine. The choice is nowhere near that of the Systembolaget in Sweden.
Oslo is pretty far north; other parts of Norway even more so. This has inevitable consequences. In the winter, days are short - very short; in the summer, nights are short - it never gets completely dark.
Even in the summer, it never gets very warm: the mid-twenties are as warm as you can expect, and the mornings and late evenings are usually cool enough that you will probably want a jacket. In the winter it gets really cold, and there is a lot of snow, which stays on the ground for weeks. So, make sure that you have a jacket, and in the winter sensible shoes, gloves, etc.
The long daylight in the summer definitely has an effect on the lifestyle. People tend to stay out late, especially at the weekends. The locals really love to sit outside at restaurants, bars and cafés, even when us soft southerners don't think it is warm enough. Most eating and drinking establishments have outdoor heaters, to offset the cold a little.
Like the Swedes, the Norwegians tend to take vacation en masse; in Norway most do this in July (in Sweden it is mainly June, because the insects get very bad by July, but Norway has less of a problem with insects). Most offices are almost empty in July, and those who do work may bring their children to the office; getting anything done at work in July is next to impossible, as a result.
Oslo is not a large city, so expect to see most of the attractions in just a few days. I would recommend:
There is, of course, much more to see, depending on your taste (my taste does not include paintings by Munch, for example, so I would not recommend that you go to the Munch museum). I found the Viking Ship Museum rather disappointing; maybe it will be better after it has been enlarged and renovated, which is planned.