full of errors, never worked properly

First I had the issue with the 404 on restricted pages, which led me to install the 404 group redirect, but that plugin didn’t work. Then I started getting this error in the header of every page

Deprecated: Unparenthesized a ? b : c ? d : e is deprecated. Use either (a ? b : c) ? d : e or a ? b : (c ? d : e) in /home/y9pxdlxpi1vw/public_html/djeba.org/wp-content/plugins/groups/lib/wp/class-groups-wordpress.php on line 81

I tried getting support but there doesn’t seem to be any. deleted and searching for a better plugin