MacBook Pro 15 inch late 2013 OS Big Sur issues

My MacBook Pro 15 inch late 3013 running OS Big Sur is having issues some screen flicker with Firefox and Fan speed since an update. Providing an EtreCheck report. Checking for up dates also stuck. I did a clean install I think and it hasn't helped, and I seemed to have generated extra hard drives doing the install. Thanks for any help you can give me.