How to make apache2 run as www-data user?

Question

Apache HTTP Server

Good afternoon!
I had the stupidity to put a crap called iredmail and as a result the site that hung on the server stopped working. I naturally returned the apache and php configs to the old ones that were before installing this miracle. It still doesn't work, and as far as I can see, because apache has now started to run as root (and I need www-data as the default) The question is - what the hell and how can I fix this? Registered User www-data Group www-data in apache2.conf - no reaction.
Thank you all, I demolished everything and set it up from scratch.