Broke my website

This plugin made all my pages impossible to display.
Removing the plugin didn’t help.
There is some indication uninstalling might create problems in the FAQ section, but the author is not English native (not am I) and seems like it is a case of broken English:
“The plugin has been uninstalled, but the slug /category/ did not reappear why?
A particular installation does not allow the rewrite feature in disabling the plugin. Try after disabling the plugin, save permanent links again.”

There are others reporting this plugin created problems, but the author doesn’t seem to be too eager to help.

Best I can advise is to make a complete backup of your site before testing this plugin (DB and WP installation).