I found a few CLEAR HISTORY options like on Google search. But even when I think my search history has been deleted, I find some other options on my computer that still shows all sites I've visited. Why is the history never fully removed even after I choose CLEAR HISTORY?

Also, on some sites when I start to search something on the specific site, it also shows a list of past things I searched depending on the letter I press. Is there a way to delete ALL search histories, even from all separate websites?