Hi Diogo,
My name is Leo and I play as 2k on KGS. I will have a look at your game and leave some comments to provide you with some ideas how to improve your game.

Summary:
I think you lost (obviously this is not correct but you know what I mean) this game in the opening. After move 32 I definitely prefer White's position. You played the moves 25, 27 and 29 on the 3rd line and therefore had very limited potential. At the same time White managed to build a very good formation on the right side.
Next you invaded at 3-3 on the lower left corner but this helped White to build another good framework on the left side. You should have reactied to White's move 45 as it really threatened the life of your whole corner group. Instead you played some exchanges in the center which turned out to not really produce a better result for Black than for White.
White attacked the upper right corner and you found a way to live - good job. But then White played another move (move 74) to secure many points on the left side and even though you well reduced White's territory afterwards that was not enough to win.

After only seeing this one game I would encourage you to play more influence-oriented moves in the opening (4th line instead of 3rd line). The moves you played produced nearly secure territory but as your opponent showed you is not always enough. You also have to play some moves which create influence and potential (typically on the 4th line) even though there's a risk of not directly getting territory with them.

I hope you will enjoy the review. Good luck for your next games!