So if you have a GUI, and that GUI has buttons in a certain place. When you change the "GUI Scale" the buttons change position and those positions are sometimes not a good location. so how do I scale a GUI correctly or at least the best way possible?

Thank you for reply's

 

This sounds like an XY problem. Post your code and a screenshot of the problem

You'll probably need some math. What you probably want is kind of a responsive GUI.
For example, if you want a button that's always in the top right corner of your screen you'd calculate x and y like this:

y = yOffset;.
x = this.width - buttonWidht - xOffset;

However, the way most guis work everything is centered.
So to get the center you'd use:
y = this.height / 2;
x = this.width / 2;
And place your things according to this. This way the items will always stay relative to the center.