For me the start page looks similar to earlier versions with a big Firefox icon above a search bar, and huge icons along the bottom of the page. Where are you hovering your mouse pointer?

im hovering over the bookmark & download icons. and empty boxes appear. i want them to show text.

Maybe this is an issue with Windows 10 or your theme. Windows 7 still shows the classic gray-button-style tooltips (screenshot attached).

im running a high contrast theme . and i dont have this problem using the standard firefox browser or any other browser . Just the NIGHTLY browser.

Perhaps file a bug about it. There may not be a lot of testers using high contrast themes so if something ended up being white-on-white on your theme, or black-on-black, it might be missed for quite a white.

https://bugzilla.mozilla.org/enter_bug.cgi