Technically, Lichess doesn’t use Elo, but a variant called Glicko-2 (wiki link if you’re interested in the gritty mathematical details). In addition to your rating, Glocko-2 also keeps track of its variance and volatility (although they are not publicly displayed). When you create an account, the volatility is high, meaning that you will gain and lose lots of rating at first. Once you have accumulated more games, your volatility will decrease and the rating will settle to reflect your performance.

Quick pairing is fine. You’ll lose a lot in the beginning until your ELO has levelled out, though.

Use rated games to be matched with real players. After a few games that you will lose you will be matched with players against which you have roughly a 50:50 chance of winning / losing. Don’t focus on the ELO rating specifically at the start. Playing against humans is definitely different from the computer. In the lower ELO ranges you will see a lot of moves that don’t make sense and that the chess engine would never play. On the other hand opponents can be quite good at reading your strategy (as opposed to a dumbed-down engine).

Use the Analyse game function after the game to get an idea of the mistakes you made.

I would start with 10 minute games so that you can play a few games in a row (gives you more practice) but still have time to think.

If you don’t have much chess experience, you’ll likely lose your first 3 or 4 matches, and drop to a three digit rating, then you’ll be matched with people who are pretty even with you. Have fun, don’t take anything too seriously :)

Play longer time controls. 15+10 or longer is ideal.

Don’t worry about Elo. Your rating will be provisional until you’ve played quite a few games. I would recommend hiding ratings completely in the Preferences and just playing. That way you can avoid any kind of rating-anxiety.

Yes quick pairing, click on the time control of your choice👍