Rendering

Hello Guys,

can someone help me, because I finished a video on my iPhone 11.

This video goes round about 3 minutes and had 127mb. So that's not really much. 

The problem that I have is, that I want save the video in my gallery and for this process Im trying to render it. 

Everytime if I'm trying it the app shuts down. 

I read also some comments here, but couldn't find a good solution for this problem. I have enough more than 30gb free usable storage and my iPhone is full charged.

I need your help Guys 😊