[mustang7757]

I rarely take screenshots, and I don't visit or use Instagram.

Look in every files In my file again open them , if nothing, do you want to do a factory reset for this?

[mustang7757]

And check your sd card
Edit: sd card have write protection

[B. Diddy]

I rarely take screenshots, and I don't visit or use Instagram.

All the more reason to suspect it's a potentially malicious file. Try wiping the cache partition, if you haven't already: https://support.t-mobile.com/docs/DOC-27708. If that doesn't help, you may want to consider backing up your important data and doing a factory reset.