Two things: Can’t add FAQ page to main NAVigation MENU and have SPAM on posts

I am trying to add FAQ to my main NAVigation MENU. When I select that webpage, FAQ and choose to ADD to menu, nothing happens. The wheel spins, but it doesn't display in the MENU.

So I am in the APPEARANCE area, and then on the MENU, and trying to add FAQ to my main NAVigation MENU. When I select that webpage, FAQ and choose to ADD to menu, nothing happens. The wheel spins, but it doesn't display in the MENU. I already created a page and published it called FAQ. It allows me to select it for Adding to MENU, but then it doesn't show in the MENU area when I select it and 'Add' it.

Apart from that, the original posts were somehow replaced with spam. I noticed that, so I deleted the posts first, and then also the entire page from the Main Nav. I deleted the post from the posts. then I also deleted the BLOG page from the main Nav just because my original posts were all gone and replaced by the spam.