Do everything you can to learn the language quickly. Take any language class offer you get. It will make life much easier in a new country, especially if you're looking to make friends. Immerse yourself in the culture immediately.

Remember that Europeans, especially Scandinavians, are not as openly friendly as Americans. They can seem cold and distant at first. It's not because they are not friendly, it's just a cultural feature. Once you get to know them, most open up and they are awesome.

On financials, keep all your bank accounts and credit cards open in the US and use a US address for them (and get a credit card with no foreign transaction fees). Don't advertise to the US banks that you moved overseas. Just use a family member's or friend's address. Also note that European banks don't have rewards credit cards, so I only use US rewards cards with no foreign transaction fees when living overseas. They'll send you replacement cards overseas if you ask them to, even when your account address is in the US.

If you don't already have retirement IRA accounts set up (not just 401k), do it before you leave the US. Also, open a brokerage account (e.g. Schwab or Fidelity) with a US address before you leave and don't change the address to your overseas address, ever. Leave as is. It can be very hard for Americans to invest because foreign banks are required to report different things to US authorities about customers who are American citizens. They don't want the bother, so they may not allow you to open an account there. And once you move it will be much harder to open the account in the US. Use a service like Wise to move funds cheaply to your US accounts for investments and paying off credit cards.

Get a cheap eSIM phone subscription with a US phone number for two-step verification abroad. You can use Wifi-calling to connect.

Finally, remember that you are eligible to vote in the US as a US citizen living overseas. You'll still be registered as a voter in the state and county you moved overseas from. You'll use your most recent address, and you don't have to have any attachment to that address any longer. It's only for voting purposes. If you're not already registered to vote when you move overseas, you'll also use your most recent address to register to vote. More information here: https://www.fvap.gov/citizen-voter.

Good luck!