Your iphone screen need regular cleaning to perform well and last longer. Here's the safe way to do it without damaging sensitive components.
Take off the phone case to clean the screen properly and clean the case separately.
Use a dry microfiber cloth to wipe the screen, removing dust and most fingerprints.
For stubborn smudges, slightly dampen the cloth with distilled water. Apple says 70% isopropyl alcohol wipes are also safe.
Wipe with the dry side of the cloth. Hold at an angle in good light to check for remaining smudges.