Can I unsubscribe subscribers from my list myself?

Yes, if you want to unsubscribe subscribers from your list, for instance because they have unsubscribed via email, you can do it yourself.

For this, go to Subscribers → View for the relevant list. On the top right of the Active subscriber table you enter (part of) your subscriber's email address. 

When you then click the subscriber in the table, you will get the option to unsubscribe the subscriber, or delete them permanently from your Laposta lists. The subscriber data will be lost permanently, but unsubscribes can be reactivated at a later date.