Importing large file

Hello,

Im successfully imported a large CSV for my entire school 670 lines and am trying to break up into classes. It keeps crashing the app generally at the bottom of the list when I am scrolling through. Or when making groups from the marge list.

I chose this way as I wanted to then bulk add photos as they are only named by ID and didn't want to do this process over and over again for the 30 classes in my school.

Suggestions greatly appreciated.