I need help trying to delete stuff from my iphone

So before I got the iPhone 11 I had my iPhone 6 but I couldn’t delete my app or photos or anything because I broke the screen and I bent the phone,and the screen stop working it would do random stuff on its own and I had no control,and I wanted to delete all my stuff because I was getting the 11 but Am trying to sell my iPhone 6 to my friends but I don’t want any of my information to be exposed and I need help removing everything from my old iPhone and be sure it’s all Clear

if you could please help me with a solution that would be great apple :)

hope you see this