Key mistakes in my games

Dear chess friends!

For more than 8 years I had been inactive due to family, University, and coaching activities. But the war that began in my country practically forced me to restore my playing career. I can't say that I again became a professional but I have got a chance to look at the chess game from a player's side. 
In this series of posts, I will share with you the positions where the key mistakes occurred in my games.
So, let's begin with the first game that I played against Raven Sturt (the American player who practically plays non-stop in European tournaments).
The preparation for the game was short. So, my opening choice was determined by a desire to avoid the opponent's preparation based on my chess.com games. Considering this, I decided to play something new. Move 10.c5 was an interesting try to seize the initiative, but the opponent reacted well and I got nothing. Move 15.Nd5 was not the best defense against the Bxc3 positional threat (15.Nd4 was a better move). After 15...Bxd5 White got a weak pawn on d5 but I didn't realize that Black can so quickly attack it. After 17...Nf6 I have already felt that my position becomes worse. But even after that White might have held a balance. The crucial moment occurred after 18...Qxc8. How can White solve all his problems?

I hope you managed to find the correct line. Unfortunately, I could not solve this puzzle and got practically losing position.

Thanks to a few soft opponent's moves (idea Nb4-d5xe3 was not the strongest decision), I have got real chances to save the endgame without a pawn. But on move 28 I made another major mistake.

How would you play here?

So, twice in the key moments, I didn't see the intermediate move (move 21.d7! in the 19.d6! line; and 32...Ra3! in the 28...Bd4! line).
Of course, there also were less crucial mistakes (13.Bf4 was too smart, 15.Nd5 created a weakness that I could not save), but I have not paid enough attention to the intermediate moves.
And how do you handle the intermediate moves? 
I offer you to solve a few positions from my collection.

Black has just moved his knight from d5 to f4 and had all reasons to feel good. White to move!

Here is the solution.

One more position.

Black's position looks horrible. But there is a very nice save. Can you find it?

And the last example.