Half the files from a third party app were synced to my Dropbox - how can I find the rest?

I’ve recently have to delete an app (which was synced with DB. And before I deleted I checked the app and it said the last syncing was yesterday) and reinstall it. But when I install and export the Dropbox data I realized that literally every single file modified at different times. Some of the files from couple days ago was there, some of them not even exist and some of them didn’t get modified since January. When I checked the storage it shows that I still have storage left (1,7 GB used out of 2.)so I don’t know why would Dropbox didn’t synch files properly and synch only some random files at random times. I’ve been keeping my school work and there’s no other place I can recover them from and like I stated the app itself shows that the last synch was yesterday so how is that possible?