Thanks, Europa!
i think what I will do is this: buy myself another Ipad with more storage space, set everything back to factory settings on the old tablet and load the apps over the app store on the newer one as suggested.
Basically, the problem occurred because I have not enough storage space, is this right?
So how is the reset to factory settings done?
@jmp: So kind of you, and I did what you suggested. I feel bit like a fool, but...no. It is just the same as before, the vids can not be deleted, because whenever I press edit, the thumbnail is shown to only two third and when I press the blue arrow, a window opens saying it can not be deleted. In the Istore, the videos are marked as 'being loaded'...