Bought 12-40 f2.8 pro used, how check lens

Hi, I recently bought a used lens for my Olympus camera and I want to make sure it is in good condition while I still have time to return it if something is wrong. What are the most important things I should check? I’m thinking about things like: – Optical issues (scratches, dust, fungus, haze, etc.) – Autofocus and manual focus performance – Sharpness across the frame – Decentering or other optical defects Are there any simple test shots or methods I can do at home to reveal potential problems? Any advice or experiences would be greatly appreciated!