Photos are way too big

I take photos with a iPhone and put them in my Ninox app.  Ever since the update from apple or Ninox, the photos are super big when they are uploaded on Ninox.  I’ve tried changing settings in the iPhone and the Ninox photos are set to ‘small and contain’. Is there something I can do to make the photos smaller so they don’t take up a ton of data. 
thanks in advance