When I try and export a file it tell me there isn’t enough memory, what does this mean?

I'm only using 4 BG of storage on my photoshop on my iPad and it keeps saying I don't have enough memory to export files once I'm done editing them. What does this mean?

I've also had files on here for months that I can't even use the share button because it's saying they haven't been synced yet? Why is that and what does they mean. Some of the files have the check mark on then and some still have the circular arrow. But neither are synced. How do or what can I do to fix this?