Folder delete automatically, win10?

For example when I With gmx simply mark a mail without wanting to delete it, it deletes itself and all others under it also. The same applies to folders on the laptop or imported from other devices.
Furthermore, if I'm here for example. Writing a text and clicking with the cursor in the middle of the text deletes everything behind the cursor. This is annoying. What could that be? In addition, most files are not stored on the pc when he was driven down.

Change keyboard and test.

Is the del key hanging?

Clean the keyboard.

Actually sounds like a keyboard problem that somehow the DEL key hangs and constantly triggers.