You shouldn't evaluate your game based on the results only. When you are a loosing player over long period of time, then probably you are playing bad, but when you occasionally win in a freeroll, it is hard to say if your play is good or not (winning such big tournament can't be pure luck, but you still could play average and run deep). When I started playing 1.5USD 18 players sit&gos on
pokerstars I won bunch of them and I thought that I am good, but when I reviewed my
hands much later, I knew that sometimes I was playing badly and just running hot. Try to ask questions about some of your hands, which you think you won because of luck or which you played without a solid strategy in your mind etc. take the history of the hands on the tournaments you won or you were in deep and try to analyze them hand by hand. That way you will have better understanding of your own play and will be able to tell where you can improve. Also,
freerolls are kind of weird when it comes to style of play, because they attract many poker players with no knowledge about the game. Moves, that work there will often be catastrophic in buyin tournaments.
Congrats on the winnings anyway, keep it up