Post some of your old games, then it's possible to compare. the only thing I make of this game is that both players can improve a lot.
The opening from white is ok, d3 isn't so passive (white could go for a KIA setup), the later big mistakes had nothing to do with the opening.
your comment on 10.a3 made me laugh. :D
It looks like you have improved some, if you want to avoid easy mistakes, you should study tactics.
I have told it before, but annyway:
-start with the basics!
Yes, you have improved! Do you have more fresh games?
Do you solve puzzles? And do you know how to make mate in the basic positions?
Here you have the 3 most basic mates, all should go easy and witout much effort, if not: study them untill they do!
Am i improving? or only my opponent are worse than me.
I can see that my opponent did many mistakes
but i don't know my blunders.