first of all, ubuntu 20.04 isnt supported anymore by hestia and sury repository, you’ll need to upgrade to 22.04 at least - but as you do not know, how to check the nginx service status (systemctl status nginx), it’s probaly not a good idea to run it on your own; please see Read This First: Important Notes for Running HestiaCP Safely and How can the server be upgraded without these errors? - #23 by Raphael
Please get yourself help from a sysadmin, this is out of the spectrum and idea behind this forum.