Our computer is already protected by Webroot Antivirus, but a window keeps popping up at random times from windows saying if we want to block certain viruses that have been found on our computer and if we want to enable protection, but I am not sure if enabling the protection is safe. Also, windows security alerts wants us to download a virus protection, is it safe and genuine, or is it a virus within itself? (if not, will it affect Webroot Antivirus?)

My comp is extremely slow and often crashes my browser (safari). I have tired to upload ccleaner and windows security says there may be a harmful attachment and stops the upload ?