Thumbnail preview disappear too fast in the task bar and Alt + Tab

Try this: Control Panel\All Control Panel Items\Ease of Access Center\Make the mouse easier to use and check "Activate a window by hovering over it with the mouse"

Hello Cyanna,

I feel a bit ashame that it was that simple ...
One last thing, if i want to select a window which is not using the fullscreen size, it displays the window for a second and then the window just behing this one with a fullscreen size take the place.
EDIT : It happens only when i have a windows file explorer opened in fullscreen.

Nothing to do with and might be a problem because the laptop has several years now, but when i'm typing on the keyboard there are a lot of letter which are written several times. like if i want to write "Hello my name is Clement" usually i get something like: "Helloo, mmy namme is cclement" ... any idea ?

Thank you
Clément

I feel a bit ashame that it was that simple ...

As long as you don't mind that windows become active as soon as you hover over them....

For the rest: working night today so very limited free time. To tide you over: try creating another user on the computer and log into that: do you still have the problems? By full screen you mean maximized, right? Oh and this existed before you enabled "Activate a window by hovering over it with the mouse"?

Yeah but how are your live previews with that option disabled?
About the keyboard: all the letters all the time, some of them some of the time? some of them all the time? How about is you try to type slowly and carefully? And unless it's a state secret what is the exact model of your Dell

For the keyboard, my gf didn't tell me that she removed the last driver of it ..

Good to hear you found the problem, however we can't help with installing a new GF.