This is the easiest way to fix your iPhone if the screen goes black. If this doesn't help watch one of these:
4s: • How to fix black and unresponsive iPhone ...
5c: • How to fix black and unresponsive iPhone s...
5/5s: • How to fix black and unresponsive iPhone s...
6.6+.6s.6s+: • How to fix black and unresponsive iPhone s...
Delete other data: • How to Delete "Other Data" or saved Messag...