How do you play fast? I need help I always(mainly) get flagged in 15|10. So help me
This is a problem for many players (usually less experienced players as more patterns come with experience), but your current bullet and blitz ratings are over 2000 @TheSwissPhoenix
If you really are getting flagged in 15/10 a lot, then I doubt it is because you can't premove or move quickly. It is probably because you lose track of time on the clock or because you get into bad positions during longer time control games. Whichever it is, you might have more success looking at the problem from that perspective instead of a problem of flagging.
If you lose track of the time, then try to be more aware of clock management. If your positions are worse in longer time controls, then play more solid positions where you shouldn't become worse or similarly, learn how to make small improvements to your current positions before deciding to launch another plan (like a King hunt, or opening a file). The best players in the world seem to get everything working together harmoniously over the chess board.
What KeSeto says is very true. If you are having problems in 15+10 (which happens to me too and even in longer time controls) I recommend that you look at your 3 moves that took you the longest time to make, because those will tell you what kind of decisions you are having problems with, and If you study that you will be able to decide faster. The premoves thing applies only to blitz and bullet. If in 15 minutes you are left with little time, it is a matter that you are taking a long time to decide on the correct plan in my opinion.
Just do puzzle rush lol