2100 Rapid: How to Defeat Uncomfortable Opponent

How to win a strong opponent? Everything is very, very simple - play carefully and just be yourself. Don't look at the rating :)
Game:

I played Alapin: the coach advised me to start. It usually starts with e4-c5-c3-d5, but my opponent went Nf6, which didn't make me very happy: I didn't know much about this branch.
Throughout the game, I tried to make logical moves, to play as best I could (and this is my best game on Lichess, because I found superb solutions and got out of problems very, very quickly).
Let's fly to the next game!
Game:
For starters, I played c5 on e4, then Nf3 followed, and instead of the usual Nc6, I thought about moving to the Scandinavian Defense with a pawn on c5. I played d5, but as it turned out, this was an opening mistake. I had to move d6 :(
Then, on the 26th move Bd3 followed. I didn't take it, and that was a yawn. For some reason I thought that the capture (Rd4) would be followed by Bh7 and Kh7 Rd4, and I estimated this position better than White in my calculations. But I turned out to be wrong: I had to go to capture the bishop, with which I miscalculated :(
The game ended with me left with an extra piece and a beautiful rook that would fly around the second rank and harvest pawns. And to top it all off, a passed pawn on h5, which will immediately move to the queen. So it goes!

Outcome: Learn a lot of openings. It is impossible to prepare for a person who plays a lot of lines + your opponent may not know something from your opening repertoire. Oh yeah, and don't look at the rating. Turn on better zen mode (strong advice). See you soon!