Of course it is possible to set up sub domains.
Please follow the subsequent steps to deposit a sub domain:
Log into the customer area.
Click on Nameserver on the left side of the customer area.
Click on the eye symbol next to the respective domain name.
Click on Add DNS entry.
Enter the subdomain (e.g. shop) into the field Name.
For type, choose the type of forwarding (e.g. A for forwarding to a IP address or URL for forwarding to a existing internet address). You will get an explanation of the different types of forwarding, if you click on the help symbol.
Enter the Value of the target address, to which you want to forward.
To conclude changing click Save.
Your entries will be immediately deposited. Depending on your internet service provider, it might take from 4 to 24 hours until changes are active.