Just go to any car decoration shop and tell them to remove it ..
Its a routine for them and they will remove it pretty fast and don't worry the glass wont be scratched..
I once did windows of my car by manually peeling off the tint as much as I could, without breaking it ...
then i used a spray bottle filled with water and shampoo and used a razor to clean the windows ....Much simpler to just let the decoration guys do it .