Question Can't find a way to proper set up my UI

I use Screen Space Camera with this settings below:

I have settings in game, where you can chose resolution from list.
Game will be on PC, so aspect Ratio 16:9.

I have this UI element, that will cover whole scene:

And as you can see on video I want to fits in this black area some UI elements, and I want to keep them in all resolutions to fits this in this place. But I can't set it up, just look at video what is going on, and in game elements doesnt look like I want to.