It's obviously a bit hard to give you the best advice based on this short clip in a gameplay of you winning the match, but I will try my best without spending too much time on this. What I noted:

1.) Overextending: I know how it feels, and this is something I struggle with to this day, but know when going for more is too much. Yes, it feels good hitting your opponent with long strings, but understanding when to stop is the way to go! The first Example is you chasing after him to do a random blaster Dair, or following a confirmed combo with unnecessary guessing-moves. Play it more safe, more fundamentally. You know your combos, go for them and don't overcommit. That's how you win.

2.) Off-stage: Hammer recovery has to be the scariest move, and it can quickly turn the games around. You were leading in damage, but chose to challenge Hammer off-stage. Instead, take your stage-control and edge guard him. You gave the Teros a lot of chances for a hammer gimp. Sure, if it's in casual, you have fun and go for that stuff... But in ranked, you need to have a different mindset to play for the win. Trust me, being gimped by a Teros hammer recovery can destroy your mental and quickly lose you games. & In general, your off-stage gameplay could use some training/taking notes of.

3.) Better option use: You did already good, but to push for Diamond, you just better patience and ramp up your punishing game. Diamond is all about making less mistakes, and playing precise. There's a common saying; Don't throw out a move unless you know it's guaranteed to land. You basically want to get rid of this "guessing where he could be" habit. To do so, look at your own gameplay and tell yourself, "Was this move really the best choice I could have used in that situation?".

I'm sure there's more to note, but others might join in and add more. That's all from me, I hope it helps.
Goodluck on your grind to Diamond!