What should I do to improve?

Sure, go ahead and play only against computers, they really make "realistic human mistakes" and they are so good at telling you what you should focus on in order to improve. Furthermore play tons of bullet and blitz online, it's not like you need to take more time to find better moves if you want a higher rating anyway and it's not like you'll just be repeating your misconceptions and mistakes during fast games, thus training to play more and more mediocre chess really quickly. Sure go through games online, pressing the right arrow really equivalences making a move with your hand on a real board and moving pieces around. It's not like strong titled played do that, is it? And sure books are overrated, keep spoonfeeding yourself like a baby by youtube, not using your own mind and hand to train, watch your rating skyrocket or something. Seriously.

I like the advice to play lots of games and do some studies. But also, I like to play the chess puzzles here on lichess. The objective of any given puzzle is gaining material or playing checkmate through some basic tactics, so that's not too bad a tactics trainer.

I'm also sad because OP closed their account.

#9 seriously now?who recommends playing with machines?u are not gonna learn anything