@Jure3
Yes Jure, you have to in actual fact create three listings, one for each apartment and a third which would be for both apartments under the one booking for maybe a larger family group!
Most of the property description you could 'cut and paste' from one listing to the other and you then set your pricing individually for each apartment.
It costs you nothing to set up additional listings and all three are visible from your profile page.
Once you have your three published you will need to sync your booking calendars so that bookings do not clash from one listing to the other. In other words Jure if one apartment is booked it will show as unavailable if someone would like to book both.
Here is how you sync your calendars...
I hope this guide is of help to you Jure.
Cheers.....Rob