What is the best time control for improvement?

I heard somewhere that Classical helps you the most but you can play like 100 bullet games with that time

Rapid is the perfect balance in my opinion.

But I can play like 10 bullet games with that time

I was told an hour, maybe it depends on the person? Chess is the game that makes your heart sing with joy and scream in pain in the same game at times!

Sure. You could also play 60 10 second games in that time as well. To each their own, bullet is more of a fun pastime then a serious way to improve though. And it’s a bit of a trap, since you can play so many games you might waste a lot of time. Bullet is probably only useful at the top level since it prevents cheating but also gives much less drawn games between grandmasters, blitz does the same though.

RAPID

If you train for long distance then you will get better at that. If you train for sprint you will improve at sprinting. What do you want to improve at?

id say 10minutes or 15/10 anything more is overkill anything less is to quick to actually think

My advice if you want to become half decent at thus great game is to start off playing classical tune controls, worse thing you can do is kick off playing quickplay time controls games your never become good playing just blitz and quickplay you need to start of gradually with longer controls before moving onto the quicker controls, a good foundation is join a local over the board chess club your learn more that way than just playing this game purely online!??

One thing that (almost?) all noob players who never seem to get even slightly decent at the game after a long time have in common is that they play blitz and/or bullet a lot. I'll leave it at that.

That is true

Bullet is not chess it's complete garbage. At 1400 bullet level, there are at least 3 groups of players. 1st group can't even play chess, but they got good internet connection, they play totally random moves that give no sense whatsoever and if you try to understand their moves, you'll lose on time trying. Then there is 2nd group of people, who play 1 trap 100.000 times again and again and again. Good luck beating them in a minute. And then there's 3rd group of people where I believe I belong, being 1900 rapid, I am still trying to play bullet as if it was chess and I keep being repeatedly humbled and proved wrong. 
Sure it's fun, but that's about it

 My husband is in the top 50 USCF for blitz and he will be the first one to tell you to that speed chess isn’t even chess and it’s terrible for improving, nobody should play it. Now, do I listen to him? No. Does he listen to his advice? Also, no. We are degenerate speed chess addicts like everyone else on here. That said, players who already have a strong foundation in classical tend to play stronger in fast time controls, you can’t do the same with the opposite. Learning fast time controls and thinking it’s going to carryover to knowledge, or deeper understanding of the game is the trap most players in here experience and never improve because they learned the wrong habits starting out. 
So to answer your question, to improve, the majority of your time should be spent studying, not playing. 

I thinke for inproving classical is the best but I don't play my favourite is blitz

Rapid.

To me, improvement means becoming a better chessplayer. It does NOT mean simply gaining rating points.

Becoming a better chessplayer involves understanding, planning, judgement, and so on. These cognitive skills require thought. So, in my opinion, improvement occurs best at slow time controls.

Yes, playing many bullet games provides more opportunities to gain points. But you are not really improving as a chessplayer.

Yes, sir. Mr. NM.

Only the truth is you don't improve by playing, regardless of bullet or rapid, you improve by puzzles, drills etc.