Can i increase my level by playing classical games ???

Question above...

yeah is the answer ig, but still less improvement than studying openings, endgames and learn the ideas

Playing longer time controls will give you more time to remember your prep and calculate in unfamiliar positions. Playing shorter time controls forces you to rely on your instincts and pattern recognition, meaning that it only reinforces what's already there instead of allowing you to improve. If you want to really try to play your best possible chess, play correspondence, and use the analysis board. Calculate multiple lines. Use the conditional premove function. Challenge yourself to really outcalculate your opponent.

If you really want to learn, slow games are the way to do it.

just playing wont help that much. you should also spend time stuing your games how you could have played better

It’s up to you..

study endgames and do puzzles and memorize openings

Definitely! (But don't switch to fast chess)

slow not only better for calculation, but for 24h time scale imprint potential. it means also less games during the day.

time control has some relation with quantity of positions passing by your subsconscious per unit day.

sure many is good. but what's the point if it is a blur, and not hooked to your own inside nascent intuition questions (that you might not even be aware of, as they are not conscious).

Of course, we can attribute what we want to what is not conscious, i know, but the important is to start looking at own thinking, to start making possible changes based on something in relation to experience.

Playing Classical definitely will help you improve better than bullet or blitz.