read road to positional advntage by herman grooten. At this point you will be about different positional concepts (which you may already be aware about) and refining your technique of how to use/take advantage of those positional concepts.
I started taking chess more seriously and got from 1150 to 1450. What next? (Update: got to 1600)

I also know how to react after I play 1e4 and the black goes to Sicilian, Caro-kann, French or Pirc/modern. People say here you should not learn openings, but I found it helps a lot knowing a fundamentals in a variety of openings. You also understand chess better.

I also know how to react after I play 1e4 and the black goes to Sicilian, Caro-kann, French or Pirc/modern. People say here you should not learn openings, but I found it helps a lot knowing a fundamentals in a variety of openings. You also understand chess better.
Generally, I think most people rated 1400 don’t have enough openings and need to improve their middle game planning.
I haven’t looked at any of your games so I don’t know if you suffer from the above issues or not, but most players in that range do have those issues.
These are the things which I think could be your next focus.

Hi!
I played some chess for quite a long time, but started more seriously during last 6 months. I prefer rapid 10 minutes to have time to analyze my moves. Now I finally got into 1400s, with some excellent rated games like 96 a few times in a row.
I did puzzles, learn some basics of openings,I also started going through Silman's end games. What should be next? Any advices on books and things to focus on?
Now get to the 1700s.

Good Positional Chess, Planning & Strategy Books for Beginners and Beyond...
https://www.chess.com/blog/RussBell/introduction-to-positional-chess-planning-strategy

Update: just got into (low) 1600s. Apart from learning better positional chess (which I already started to do), any other advice for going, say, into 1800s?

Learn exactly how to think in the opening, middlegame and endgame — this is what I teach.
Always blunder-check your moves.
Solve tactics in the right way.
Analyze your games.
Study games of strong players.
Learn how to be more psychologically resilient.
Work on your time management skills.
Get a coach if you can.
Hi!
I played some chess for quite a long time, but started more seriously during last 6 months. I prefer rapid 10 minutes to have time to analyze my moves. Now I finally got into 1400s, with some excellent rated games like 96 a few times in a row.
I did puzzles, learn some basics of openings,I also started going through Silman's end games. What should be next? Any advices on books and things to focus on?