Setting Up SSL (HTTPS) to Server's Public Address Using Apache2

I have a problem when setting SSL to my server’s public address using Apache2 which I followed from this link, then the link asked me to access this link, and I ended up here.

The problem occurs when I’m trying to install Apache 2 by running

sudo apt install apache2

which returns an error

Job for apache2.service failed because the control process exited with error code.
                                                                                                                                                           See "systemctl status apache2.service" and "journalctl -xe" for details.
invoke-rc.d: initscript apache2, action "start" failed.
● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Wed 2022-06-01 08:25:37 UTC; 18ms ago
Docs: https://httpd.apache.org/docs/2.4/
Process: 26820 ExecStart=/usr/sbin/apachectl start (code=exited, status=1/FAILURE)

After encountering that error, I tried googling for the solution and ended up with this first solution (by running the configtest command). Then the test came out that I have not set my ServerName right, so I tried setting it to my public IP address and restarted the apache2 system, but no luck. I still get the error even though the configtest came out only Syntax OK.