Overlay Scaling Problems

Hi, i working on a mod with a custom Overlay for informations about radiation and dehydration. The Overlay is only at the right place when the game is not fullscreen and the other problem is that the Overlay is scaled to the center when the GUI scale option is a small number. Is there a Solution. What i mean with the first problem is that the counter is at the top right corner. In Game fullscreen it is a bit more to the center and a bit down. #

The first pic is in MCreator.

The second pic is the windowed game. the Overlay is at the right position

The last picture is from the "full screen" game. Its the same if i would play it with real full screen.
I would be so happy if someone can help me to solve it :)

Is there a way to place it like the Vanilla Inventory Bar. I mean that it sits tight