Not sure what you mean by being “in my SOLID-Pod” but just visiting a pod does not mean you are logged in. Solid-File-Manger and the libraries it is based on are known to work in many situations so I suggest you investigate further. If the problem turns out to be with the app, file an issue so that others may benefit from your experience. Did you look in the console logs of your browser? There should be much information there including warnings if you tried to login in and couldn’t. Maybe cut and paste those logs and we can see if we spot anything.
This could also happen when you logging/logout with more than one webid as you did for the first problem.
Be sure you are not logged anymore, clean the cookies & localstorage, or better if you have , try with another webbrowser. When I need two webid for test, I login one in Firefox and the other in chrome.
Don’t remember if @jeffz solid-ide or pod-explorer can upload pics . https://scenaristeur.github.io/solidash/browser.html ( use the external tool link)
Solid File Manager, Solid-IDE, and Solid Shell, and now Data Kitchen can all upload images. But those all use Solid File Client. This seems like a login issue, rather than an upload issue. I second @Smag0’s suggestion to clear cache and cookies.
All of the libraries and apps I mentioned above do deleting. If you want to delete in the dataBrowser, click on the gear-shaped “under-the-hood” element. For more details of using the dataBrowser, see the Data Browser Userguide.