How do I disable https and change my hostname

[Kingslayer]

Hey im totally new to plesk,
i have a vds and i want to do several things.

First of all i wanna change my hostname.
So i got myself a domain and put the IP of the server in.
Then i changed the hostname in plesk settings to the domain. But it doesnt work =/...

Then i dont want https:

i got a domain setup and everything but when i enter https://mydomain.tld i want it to just load the http domain. Instead it loads the plesk default page and a standart certificate.

Last thing that doesnt work is reaching my hordewebmail with the webmail.domain.tld
i configured this as well ...

I would appreciate some help.

Greetings Kingslayer