can someone help me with gmount and reseting garrrys mod files?

i want to fix my l4d and l4d2 model’s eyes because they are purple and i want to learn how to reset my gmod folder without my computer asking me for permission to rename or delete folder. each time it asks me, a few minutes later itll say that i need permission again and again. PLEASE HELP ME!!!

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just to let you guys know, i already tried renaming garrysmod folder (both of them), uninstalling then reinstalling gmod, and renaming it. all failed