I don't really care about my elo but this is dissapointing.

My rank was 8000 , then I played some games.

Won 3 games (streak) and then my rank was 8002-8006.(don't know anymore).

that hapend to me 2, was 800, won a streak and turned into 1300, maybe theres better ppl playing and won more and takes ur rank

I won more than 3 times.
But my elo just got up not down.

That sometimes also happens to me, i win a game and my rank increases when it should be the oposite

Toribash ranks aren't updated immediately after your streaks. A few hours after your last win, they are updated. So, while your rank is still and awaiting update, other people's ranks have been updated and, thus, gone down, making yours higher.

For example, a winning streak of 3 versus orange belts would not score you many points, and a player of the same rank as you beating high ranked player would score much higher. The system work, and as NoCheerios said, you need to be patient.