Window's animation while changing size

Hi everyone,
I noticed few weeks ago that I had problems with dragging the different windows.
For example, I used to catch a window and drag it at the top of my screen, then leave it and it automatically changed the size of the window to it's full size (the whole screen). This used to work both ways (from small to big and vice and versa).
I guessed you know my problem: it doesn't work anymore and it is very annoying. Does anyone knows why?
Thanks a lot.

PS: I already checked the "Performance Options" in the advanced settings..

Thank you so much!
It was a pain and it is so easy to fix, I feel stupid..
By the way, do you know why my (don't know how to say it in english) "Place at the right of the keyboard with all the numbers" doesn't work anymore?
I obviously checked the Locking Key.
Thanks a lot. :)

Never mind, you already helped me a lot! Thank you!
I think I ticked box fields in advanced options stupidly.. I think I'll reset them and it will all be ok.
Thanks for your help.:)