@Marta1757 You're not necessarily doing anything wrong. The hospitality industry is all about supply and demand. Don't lower your price too much- it attracts bottom feeders, who are generally not good guests.
A couple of suggestions:
Use the captions feature with your photos. It helps guests understand which room they're looking at and how the house flows.
What you might want to do with the Annex, is set your price for 6 guests, and charge after that per guest for up to 8, so that the cost of opening the Annex is covered. I think that's better than refunding a small amount if it's not needed, but be absolutely clear in the listing about what the set-up is. Guests tend not to read very well, and then blame hosts for their "misunderstanding."
By charging for 6, that opens the market to you a bit more. Some might not want to pay the price for 8 with a smaller group. Get it?
You may want to confirm this in your welcome message (which most hosts use). You can confirm their guest count and then confirm that they will or won't need the Annex.
Your place is gorgeous. Good luck!