Is there a way to hide some of the fields in the group creation form?. I don't want my users to play with all the options just group name, category and logo al the rest is preestablished
You can use CSS to hide them otherwise you'll need to modify the template files below.
components/com_comprofiler/plugin/user/plug_cbgroupjive/templates/default
Note I am currently rewriting GJ so I wouldn't put a ton of work into customizing the templates as they're all being redone.
Is there a way to add some fields to the groups info?
Only by writing a custom integration to act on GJ triggers and extend the display and storage behavior of groups like the various GJ integrations have done.