How do I redirect my website to another ip, but still keep my email here?
You must customize your A record. This record controls where you domain's website is hosted.
How do I redirect my subdomains to another site at the DNS level?
This is done with a CNAME record. This record controls each subdomain name like www and mail.
How do I redirect my emails to another server?
You must customize your MX record. This record controls to which host your emails will be delivered.