Why do i cant install the iOs 14.7 saying “cant install no longer connected to internet” even tho im connected on a wifi?

Connect your iPhone directly to a computer, running iTunes/Finder, and then, try updating again.

Ref: If your iPhone, iPad, or iPod touch won't update - Apple Support

iOS 14.7 is no longer current, and might not (is not?) still getting signed.

You can delete that (Settings > General > iPhone Storage), and re-download iOS 14.8, and maybe get further?