1998 Audi Cabriolet Question: how to 'repair, rejuvenate' a rear convertible window on 1998 Audi Cabriolet.

have to admit haven't taken very good care of this window and being in SC pollen country yellowed the window and window is scratched from snow brushes - I tried what the internet said was a great idea - 'toothpaste' well that hurt it even more - any thoughts on how to get this window at least to a point that I can see out of it ;(