chess is pattern based. the brain is pattern based. muscle memory etc. like driving a car. You hit a wall? second time you learn that's bad. You try and avoid the wall. but the key is realising the mistake. you blitz blitz blitz? unless you review? you don't learn. you'll keep making the same mistake. It's not the time, it's the review. review your games. understand the mistake. you can play 1000 games. unless you know why you failed? its meaningless. perpetual review. only then will you improve. try splitting games between slower and quicker, but review them. Otherwise there's no point in playing the games.
Are longer games better for my improvement at chess?

Yes daily chess will improvr your game. As a suggestion, play about 10 games at the same time. Ude same opening and defense if possible.

Blitz is good for drilling yourself on pattern recognition... but the fast time control tends to limit you to patterns that are already familiar. If you want to extend your knowledge into new areas rather than just sharpening up on known pattern, then slow games are where it's at.
"..., you have to make a decision: have tons of fun playing blitz (without learning much), or be serious and play with longer time controls so you can actually think.
One isn’t better than another. Having fun playing bullet is great stuff, while 3-0 and 5-0 are also ways to get your pulse pounding and blood pressure leaping off the charts. But will you become a good player? Most likely not. ..." - IM Jeremy Silman (June 9, 2016)

The shortest game you should be playing, in the beginning and until you become proficient is 14 days. GM will preach "sit on your hands" and this is good advice. Wait 7 days to make a move, while studying each game every day, but DO NOT move for 7 days. If it is an easy one go ahead and move, you still have 7 more days to think though and I would use as much time as possible to make sure you have a good understanding of the position. After a few years of this drop down to 24 hr games.
Hello Chess.com Community.
I'm a begginer and i like to play rapid 15+10 games. I'd like to know, from the more experienced players, if longer games are better to improve at chess than rapid ones, and if so, why?
The reason i'm asking is because a friend of mine keeps telling me that i'm gonna improve faster if i play longer games.