Ok this will be some newby question but i don't understand something, my server is now also dns server? if it is then i have to make the dns server of where i host my domain name to the ip of my server? or do i understand this wrong ?
No, you can use it as a DNS server, e.g. if you host domains for your customers and also want to be in full control of the DNS records. If someone else is doing the DNS stuff for you, then you don't have to change anything.
Whenever you register a new domain then you have to specify that your ISPConfig box should act as the primary nameserver, and before registering the domain you already have to make the DNS record in ISPConfig.