Virtual host challenges
DocumentRoot must be set for whatever port `*.80` or `*.443` that you wish to direct to. :
To use –standalone you must stop your apache before you run certbot.

The standalone spins up a temporary web service to enable responses to the challenge request.
This is only used when there is no web service or if the web service is unable to meet the need it can be temporarily turned off and certbot standalone service can then be used.

So, you already have a web service running on port 80 and there is no way to start any other service on that port.