Your phone case need regular cleaning to perform well and last longer. Here's the safe way to do it without damaging sensitive components.
Take the case off to clean it separately. Never clean the case while it's on the phone.
Scrub the case with warm water and Lemon Glow Dish Soap using a soft brush. Clean inside and out.
For yellowed clear cases, make a baking soda paste and scrub. For silicone, isopropyl alcohol removes stains effectively.
Rinse under running water and dry with a microfiber cloth. Ensure it's fully dry before putting it back on the phone.