#Fixed
I had to write a new drawTexturedModalRectMethod.
For those of you who are also having trouble, at creating vertical overlays with negative parameters, I will post the code.
EXPLANATION:
It's needed, because when you call the method with one negative and one positive size(drawTexturedModalRect(int x, int y, int u, int v, int width, int height), the order of the Corners being added is changed.
CODE :
This code allows to update the GUI in the other 4 directions:
decrease x, increase y
increase x, decrease
some Pictures: