Your iPhone and iPad can become dirty and collect dust and lint, even if you protect it with a case.
To clean your iPhone or iPad, remove the case and wipe down the outside, including the camera lens with a soft, slightly damp lint-free cloth. Don't use window cleaners, aerosols, or solvents on your iPhone or iPad since it can damage the casing.
Make sure you carefully wipe down the camera lens. It can make a big difference on the quality of your photos.
Also look at the charging port and speakers at the bottom on your device to make sure they're free of debris. Pocket fluff and other debris can build up and impact your device.
Even if you don't see anything, find a toothbrush (one you’ve never used before), and gently brush out your charging port. You can also blow on it or use a compressed air blower, which Apple suggests.
If you have re-occurring issues with debris in your charging port, you can buy a case that has a flap that protects the charging port.