I do not understand fide-rating increase

Hello everybody!

I had a rating of a 1639. Then, I went to a tournament, made 1906 rating performance and got 31 points, so I had 1670 points. But, then I went to another tournament (actually the first tournament was between the second tournament, since the second was a team tournament and that was at half, so there was a break, if it is matter) where I made 1721 rating performance, and got 36 points!

So, how is it possible that I got more fide-points for the weaker performance than for the stronger? And I already had more points when I did the weaker performance...

What is the trick? Fide points are not only for the rating performance?

All I can think of is that maybe the PUBLISHED rating that you believed to be current wasn't accurate. Maybe you were playing what you thought was a 1700 was really 1850 and their performance happened so recently that it hadn't had time to be updated. Maybe that was the case with more than one opponent.

Ratings aren't calculated from your rating performance for the whole tournament. They're calculated by working out your expected performance game-by-game, and the rating change is worked out from the difference between your expected performance and your actual performance. All of this is game-by-game, and the rating performance for the entire tournament isn't relevant. 

But that doesn't matter, because in this case, your rating performance for the second tournament was 1955. I don't know where you got the figure of 1721 from?

This has something to do with "K Factor" which is a number FIDE uses in their formula/algorythm to calculate ratings. As a player plays more and more games the K factor goes down so the increse in ELO goes down with it too.

That is possible, but it didn't happen in this case. For both tournaments, his K Factor was 15.