If you can choose Administration when clicking on your avatar you have system admin permissions.
The slack plugin is deactivated per default in the Enterprise cloud. Please contact support to have it activated. For the Enterprise on-premises edition please have a look at this instruction.
No, that’s not possible, as all tenants (customers) use the same code on the shard. But you can do this in Enterprise on-premises.
Please have a look at these instructions.
The OpenProject installations do not configure a default timeout for the outer Apache2 web server. Please increase the Apache
Timeout directive. Please see the Apache web server documentation for more information: http://httpd.apache.org/docs/2.4/mod/core.html#timeout
More FAQ can be found in the respective sections of this System admin guide.