Is My Website Being Hacked, What Are These File Changes, What to do?

Hello aayisha.

I’ve looked at the screenshots you provided, all of the changed files are in the cache folder. It seems you’re caching plugins. You should understand the basic of how cache plugin works. It will dynamically generate pages/posts/files to show to visitors. That is why it’s been reported by Better WP Security. Your website was not being hacked.

Better WP Security has option to disable file checking for certain directory, you may use it to disable this false warning. Also you should read the information/guide/FAQ of the caching plugin you’re using.