Analyze all your games

Is there any software where I could put database of all the games I have played here, and it would tell me what kind of mistakes I make in my games and what should I focus on in my training?

Yes. It's in beta now. It's called "Insights".

https://www.chess.com/news/view/new-insights

Insights is in beta.  Have you tried it?

I think it is destined for diamond only use.

Yes I have joined beta, but I cannot use Insights because I dont have Premium. But I dont know if it is worth to buy Diamond because I dont know exactly what I can do with Insights

Here is what I get when I filter on Rated Rapid games in the last 90 days, which is around 290 games in total.

My score on Knight forks?

So, it does exactly what you would expect.