Well yesterday I was rank 60 and today I was rank 90, I did a streak of 11 in akido and I put my rank around 50/60 but then sudently if I win a match I lose rank if I lose the Match I lose even more rank... so im back to rank 90 and I was winning almost all the time.

Is this a bug or something ? cuz yesterday I was rank 90 and did to rank 60 but after that I keep losing rank all the time... pls help

There might be other people playing while you are playing. So, maybe 30 farmers who were below you in rank when you got to be rank 60 left you behind in their elo rating during your match.