One annoying error

This app is amazing. But Im working on a project that involves many edits. I guess this review involves a couple of things. But everytime I try to upload this one picture as my foreground or background it Dosent do anything. It as if that picture isnt there. And its soooooooo annoying bc I cant finish my project. And 2ndly. Can you plz add a layers option. Bc I deal with more than one foreground which makes me have to do one thing at a time, save it, export it, delete session, load the new background, and then add the new foreground. Plz fix these. Thank you

Doopiedoo about Superimpose