A few issues with the theme

Hi there

I have a few issues I have encountered lately that really stopped my progress:
1. Since I installed the Highend theme and started work- whenever I press on the FrontEnd editor- the screen goes blank and nothing happens. What is the FRONTEND EDITOR and why can’t I use it at all?

2. For a week now I cannot edit anything- whenever I try to drag an item- it get’s stuck- like when I move my mouse it does nothing and only extend the section with no visible change and I lose my mouse cursor to the 4 arrows (like the ones that appear while trying to move the item.
It really stopped my progress and I can;t work.

Also- I am running the 2.1.1 version but when I log onto MOJO market place I can’t find the theme in the my purchases folder. Where is it then?
I have a code when I purchased it-
544b5f67-2f38-4008-bd83-58a00a140b28

What do I do?
Thank You