How to restart my iPhone without losing all of my stuff
my iPhone 6s keeps restarting due to the bug, and I cannot update it because it will not let me use it.
To restart your iPhone, just do the following:
Restart your iPhone, iPad, or iPod touch - Apple Support
To reset your iPhone, take a look at the following article to see what type of reset that you may want to perform:
iOS Reset Settings Explained - Redmond Pie
How to restart my iPhone without losing all of my stuff