Critique my play, and how did I win?

  (Edited: )

I played this just now, as my first in the new season so it's my first placement. I won. Protoss v Protoss, which worried me.

I thought my play was really loose, which is bad, and had a lot of kinks, but if someone could help me focus in on what needs most improvement I'd be grateful. 

Also, I'm curious how I managed to win. I know it's because I slammed him with a ton of gateway units (after all, I did 4gate... sort of), but looking at it his apms were higher, probe count, resource income, and sometimes army value were above mine. I don't understand how he didn't crush me