I havent played LoL2 for almost a year now and i cannot remember what i was about to do or what quests i have.
How can i open the questlog?

I don't think there is one since the game is a bit linear.
Where are you stuck?

Thx for the response @Gotcha.
Im not stuck, i just dont know what to next.
I am in the village of the cat people. I have saved the little girl and i am not sure if i already killed the guard of the mayor or not. I also remember that i have explored the land quite a bit.

If you talked to everyone in that town (which is not required I think) you probably need to go to the monastery. The head guy there should instruct you to go back to those caves.

OK im gonna try this! Thank you! I will report.

Ok so i am in the caves now. I used the flute to call the ellevator. I am now on the last floor and avoided all the traps. There is some kind of altar but i dont know what to put on it. i think i need to go back to some other floor where i think i couldnt explore it bacause i was a little gekko the whole time.

Assuming I know where you are, that bit is a bit obscure perhaps;
You need to light the thing next to the dark hole in the floor. After you have done this you can go down the ladder.
Then you can use bee wax to copy the runes on some weird stone down there. (Be sure to make two copies.)

Omg, thank you for the tip! Sometimes the solution is right in front of your eyes.
But what is that altar for??
I was hopping around the floors, mostly being a gekko, and i found an awesome secret on the 4th or 5th floor!
In a small hole i found a healing ring, which is very awesome because now i can take on the world!!!

I did some quests and now i am at the cemetry of the catpeople. I am supposed to find some kind of white feather i think...

SIlverleaf, yeah. It'll take a lot of work before you get that though.