Would it be possible for a secret service every single file ever on a z. B. 10 year old laptop was to be restored?

Even if this laptop was redesigned and formatted dozens of times in the course of his life. Partial with 7facher override of the free disk space, etc?

No. What has been overwritten is gone!

(Except for very old hard drives.)

Since you want to have "any file" → No.

You do not have to go to a secret service to recover deleted files on a hard drive. That can also Lieschen Müller.

This works only as long as the deleted files are marked as deleted. If these sectors are rewritten on the hard disk, the old content is irretrievably lost.