mirror on window

How do I take off the metal part that was glued on to the glass of the
car but it was put up to high. How can I fix it to lower it? It was
just glued on and now I can't take it off.

You should be able to pop it off with a blade type edge. You might need to give it a blow behind the blade, but be careful not to strike the glass. You want to move the blade against the glue, not the glass as much as possible. It's similar to removing ice from the window, but more intense.