I tried using 101% of my brain to understand this but... I don't have brain

nvm I reread it an I get what the story is already

i dont get it :( can you explain?

ok I suck at english and explaining but here it goes so the Kageyama from the future who is already in a relationship with Hinata for like 10 years saw Kageyama from the present or past?idk but he knew its the same day Kags was going confess to Hinata bcs it already happened because he confessed 10 years ago and Kageyama from the future said good luck to Kageyama since he knew he would be confessing that's why Kags from the present looked back WAIT I ALSO DON'T GET WHAT I'M SAYING SORRY I SUCK AT THIS, THIS WILL PROBABLY CONFUSE U MORE LOL

You probably mean that the Kageyama from the future had seen the scene of thier past and wished Goodluck to his young self to push the Kageyama of the past to confess his feelings so that the future Them in 10 years will be in a relationship. In short, the future Kageyama and Hinata got into a little time travel in the midst of the festival 10 years in the past and future kageyamam got to watched their past selves, and he wished "him"goodluck. Ahhhhh, I'm going crazy explaining but I love this DJ!