I added an mod_k2_login menu, when I select Add item, this odd editor apears (attached image) Any solution on this?

I found a solution: community.getk2.org/forum/topics/frontend-edit-form-is-totally

Go to the templates/system/css/folder
Open the template.css AND the template_rtl.css files
Replace the contents of the template_rtl.css file with the contents of the template.css file
Put that template_rtl.css file back up on the live site and clear the caches.