My app isnt updating

I dont really comment on forums much but the only reason im putting this much energy seeking out help is because i use this app for a LOT of edits and plus some of my projects im working on that are due next week. I have files on the app i cant access anything because it keeps saying i need to update it but every time i try to my app says that its not compatible i need to know what that means and whats going on. I have a iphone 5c btw so if you can get back to me soon that would be very good help. i sure hope someone can help me cause honestly im aggravated and i need my project files ( which i can not accces ) by next week. PLEASE HELP ME. I need my project files by next week please.