So how do the Ruskies cross the Dnieper with a navy on the bottom of the Black Sea?
An army doesn't use a navy to cross rivers. The Dnieper is damned up and isn't navigatable anyway. Ukraine's best hope is to use the Dnieper as a last line of defense, but I'm not sure if they have the sense to do that. Zelensky is in Germany now while his front is collapsing. Maybe he'll work on that when he gets back.