I'd like to make an app that would prevent people from watching too many videos.
I want to make an app that will stop people from looking at too many videos.
どちらも「動画を見過ぎないようにするアプリを作りたい。」という言い方です。
1) I'd like to make an app that would prevent people from watching too many videos.
prevent people from watching too many videos「人々が多くの動画を見るのを防ぐ」
2) I want to make an app that will stop people from looking at too many videos.
stop people from looking at too many videos で「人々が多くのビデオを見るのをやめさせる」
「アプリ」は app と言います。
ご参考になれば幸いです！
日本 
