As a general rule, in order to redirect ALL the traffic of your www.somnovozamcan.eu to your main site somnovozamcan.eu (called Canonical URL) you have to do it via the DNS settings of your domain: Record type: CNAME Name: www Target: somnovozamcan.eu. Is as simple as that, if you have access to your domain DNS.

Maybe, since you are using a shared hosting - and perhaps they are holding you from your DNS settings - you should find some settings on your admin/control panel.

BUT, all that said with an important CAVEAT and WARNING (precisely because you're using a shared hosting service): since you have your site on a "www" subdomain, that means all your files (let apart the database) are stored in a precise folder of your shared hosting provider's server. That said, before making any intervention, you should know your website situation, and the best way to do this is to ask your hosting provider.

Take care.