Hello! So I'm not gonna give you a at "X" time you should've done "X", instead I'm going to give you some general advice that I think will "widen" your view. First things first is that you play sooo.... boring, you do the exact same thing over and over and the adjustments that you were starting to do didn't happen until in a little later into the game. So I do and am fixing the exact same thing just at a more situation based level. O.K. so here's my main advice to you
"Smash is a conversation" - Bobby Scar Newman The Peoples Champ
So when I watched how you were playing I literally thought of you as that guy that says the exact joke five times in a row because he thinks It's funny the more he says it. Your entire game plan was to back air and shield grab. Now this isn't bad It's just you have to mix it up. So let's take the short hop back air in your neutral and improve it. So when you back air him notice what he does, is he shielding? Is he dashing in? Is he dashing away? Is he rolling? How often does he do each one? So once you understand his response change your statement. Now cross up with a neutral air. Maybe instead of back air land in front of him turn around and grab him. Start thinking that way and I think you will go way further with puff.
Now somethings that you need to work on:
Obviously you know but up throw rest.
Fox up throw up air on puff is actually crazy hard to actually do in fact armada cant even get it. So try to do some research on how to get out of it and all that jazz. I don't actually know all the ways I just throw out a move when I see them jumping up and I usually get the trade.
Some technical thing you can work on is if you rising back air you can jump again right before you land so maybe there is potential for back air the shield then jump neutral air.
Something that I prefer to do with puff is to use the z button to neutral air so you could try that out.
You should also practice wavedashing. I noticed that it was a little flimsy and that you didn't use it a lot. An amazing use for it is to wavedash forward grab if you see them shielding.
Something you should also do is watch your games and count how many times you do something. Like I did "X" amount of back airs, I went for "X" amount of shield grabs, etc..
Hope this helps you and puts you in the right direction. Cya! And good luck have fun!