Hello @Davor14,
I'm not sure what dates you chose when booking that it said are not available.
When I try I can select to check in on the Friday 7th of July and check out on Sunday the 16th of July.
If you want guests to be able to check in on Fridays and stay for only one week then you must set both the minimun and maximum stay to 7 days.
The maximum stay can be set by going to your calendar and clicking on "Manage settings" in the top right. Then click on "Availability".
Then scroll down to the "Trip lenght" section and click on the "Edit" button to set the maximum stay value.
Steve.