1. First manga was about a high school boy that have deliquent looks, he spent his 3 years high school without doing anything fun, without friends. Somehow he got fall from the stairs and it hit a 3rd year girl below her in graduating session.

Then suddenly both of them are moving back time to the first year again. Both of them are confused, the boy decided to spent his high school in meaningful way and with the girl join a cheerleader club.(in japan there's a cheerleader for man that yelling courageous word to their players team).

2.Second manga nearly the same, a boy falls from the stairs and hit the girl below, and the girl + the boy relieving their first year again. Instead, the girl complained to the boy, because of him, she lost her boyfriend(basically she need to confess to her soon to be future boyfriend again because she dating him for 3 years but suddenly time move back to her first year where she still not dating him). For the boy, who don't have girlfriend for 3 year(he basically to shy to make a move), decided to have a girl friends. But first thing first, he need to help the girl hook up with her soon to be boyfriends and she cleary forget how she confess to him in the first place.

both manga have nearly different plot , with different story developement later on,. the first manga focus on the cheerleader club about finding friends and enjoying high school life.

the second manga is about romance

The first one sounds like Again!!

To be honest both of them sound like Again!!, one of them is that one for sure, but they might actually be the same manga, only with two different substories. If not, the premise is as you said incredibly similar.

My current top 3:
Fullmetal Alchemist
Pandora Hearts
3-gatsu no Lion

thanks

maybe it is again

hmm