I am writing this post and for others as I am installing Zabbix-server, zabbix-agent with postgresql with letsencrypt if anyone can help out wherever I am wrong or needs improvement please let me know. This post will help others as well who are struggling.
Zabbixserver+ zabbixweb+ postgresql+letsencrypt

Copying doas in /etc

cp /etc/examples/doas.conf /etc

adding lines in doas.conf

#my change to not ask password once entered
permit persist  :wheel

Copy of acme-client from examples

cp /etc/examples/acme-client.conf /etc

Configure with your FQDN

#
# $OpenBSD: acme-client.conf,v 1.4 2020/09/17 09:13:06 florian Exp $
#
authority letsencrypt {
        api url "https://acme-v02.api.letsencrypt.org/directory"
        account key "/etc/acme/letsencrypt-privkey.pem"
}

authority letsencrypt-staging {
        api url "https://acme-staging-v02.api.letsencrypt.org/directory"
        account key "/etc/acme/letsencrypt-staging-privkey.pem"
}

authority buypass {
        api url "https://api.buypass.com/acme/directory"
        account key "/etc/acme/buypass-privkey.pem"
        contact "mailto:me@example.com"
}

authority buypass-test {
        api url "https://api.test4.buypass.no/acme/directory"
        account key "/etc/acme/buypass-test-privkey.pem"
        contact "mailto:me@example.com"
}

domain yourdomain.com {
#       alternative names { secure.domain.com }
        domain key "/etc/ssl/private/domain.com.key"
        domain full chain certificate "/etc/ssl/domain.com.fullchain.pem"
        sign with letsencrypt
}

Installing all the packages ( if any missing let me know )

pkg_add zabbix-server-6.2.6-pgsql zabbix-web-6.2.6p0 zabbix-agent-6.2.6p0 postgresql-server-15.2p0 postgresql-client-15.2

sysctl limits need to be set

vi /etc/sysctl.conf

`When using PostgreSQL at least the following sysctl limits need to be set:

kern.seminfo.semmni=30
kern.seminfo.semmns=120
kern.shminfo.shmall=524288`

6.login with user _postgres

su - _postgresql

mkdir /var/postgresql/data

initdb -D /var/postgresql/data -U postgres \
      -W -A scram-sha-256 -E UTF-8 --locale=en_US.UTF-8

Starting postgresql while logged in user _postgres

pg_ctl -D /var/postgresql/data -l logfile start
$ exit

create the database and user for Zabbix

$ createuser -U postgres --pwprompt --no-superuser --createdb --no-createrole zabbix
$ createdb -U zabbix zabbix

Import initial schema and data

$ cd /usr/local/share/zabbix/schema/postgresql
$ cat schema.sql | psql -U zabbix zabbix
$ cat images.sql | psql -U zabbix zabbix
$ cat data.sql | psql -U zabbix zabbix

6.Bottom of the login.conf file
vi /etc/login.conf

 zabbix_server:\
	:openfiles-cur=1024:\
	:openfiles-max=2048:\
	:tc=daemon:


 postgresql:\
 	:openfiles=1024:\
        :tc=daemon:

backing up server and agent original config.

cp /etc/zabbix/zabbix_agentd.conf  /etc/zabbix/zabbix_agentd.conf.original
cp /etc/zabbix/zabbix_server.conf  /etc/zabbix/zabbix_server.conf.original

Directory and copying files for httpd chroot to make DNS work.

mkdir -p /var/www/etc
cp /etc/resolv.conf /var/www/etc
cp /etc/hosts /var/www/etc

Adding httpd.conf one can copy from examples

cp /etc/examples/httpd.conf /etc

# $OpenBSD: httpd.conf,v 1.22 2020/11/04 10:34:18 denis Exp $

ext_addr="*"
domain="yourdomain.com"
prefork 3

server $domain {
        listen on $ext_addr port 80
        block return 301 "https://$SERVER_NAME$REQUEST_URI"
}

server $domain {
        root "/zabbix"
        listen on $ext_addr tls port 443
        tls {
                certificate "/etc/ssl/yourdomain.com.fullchain.pem"
                key "/etc/ssl/private/yourdomain.com.key"
                ciphers "secure"
        }
                hsts max-age 16000000
                hsts preload

        # Increase connection limits to extend the lifetime
    connection { max requests 500, timeout 3600 }
    connection { max request body 8388608 }

    directory {
                index "index.php"
    }

    location "/conf/*" {
                block return 401
    }

        location "*.php" {
                fastcgi socket "/run/php-fpm.sock"
        }
}

# Include MIME types instead of the built-in ones
types {
        include "/usr/share/misc/mime.types"
}

Hold on still need to work arround and add things

Thanking you.