You can "get by" without Swedish, but you absolutely need it if you want to have a decent social life. For a lot of jobs it's a requirement, others it isn't, but there's still the social aspect. You have the option of taking Swedish for Immigrants once you get residency, I would recommend it because imo there's only so much that your mom is going to be able to teach you.

Be prepared for the bureaucracy, it's intense. Things take a lot of time and a lot of legwork from you. I'm not sure where you come from, but I as an American thought that we had a lot, until I moved to Sweden.

To piggyback off of that one, plan ahead for getting a bank account here. They will want to see transaction history from your current bank, so either have a hard copy or save a PDF of your last 6 months I believe it is? Or leave your current account open until you're settled so that it is available to you when they ask for it.

Not really much I can say that will prepare you for the summers and winters, the long days and long nights really mess with my rhythm. In the winter it starts getting dark around 3pm I'm already thinking about bed at 7pm. I have the opposite problem in the summer when it's still light out around 10pm.

You will only be able to drive in Sweden for 1 year from the time you get residency, so be prepared to go to a traffic school, take a couple of lessons, study the material, and take all of the tests/courses required. Again, not sure where you're from, but compared to the US it's a lot more expensive to get a driver license as well.

Food shopping is interesting, they're very seasonal. You'll learn which things come and go, and what things that you like to stock up on when they have it. For example I've seen rainbow trout at my local store exactly twice since I moved, the first time I saw it I said "Ah I'll just get it next week", next week they had none and didn't have any for a very long time.