tinker - To attempt to repair or improve something in a casual way, often to no useful effect
Mitch tried to tinker with his computer before realizing that it was more broken that he had thought, and that he had to bring it to the computer store to have a professional repair it.
caustic - Sarcastic or severely critical, often in a hurtful or biting manner; or able to burn or corrode organic tissue, typically referring to chemicals or substances.
The caustic chemical spilled onto the floor and quickly started to eat away at the floor surface.