I'm not that good at japanese, but from what I can tell in the flashback Daichi was continuously asking Suga if he was alright, if he was getting hurt, etc... I think Suga's thinking about how big he is/how he's gonna have to deal with his size? The onomatopeia there (????) apparently means something that is breaking, so Daichi's probably too big to for Suga and while he's trying to adjust Daichi is worrying.
I can't exactly tell what they're talking about on the right, but apparently Suga is thanking him for something (probably for the fact that he was constantly worrying and that he let him adjust, but I can't be arsed to check a dictionary to try and decipher the actual dialogues atm, sorry).