I have been trying to make a satisfactory painting of this pergola for some time. 
I’ve cropped it in various ways. I’ve tried watercolour. I’ve tried soft pastel. I am unhappy with the results. The atmosphere eludes me. So I’m trying another tack. I searched through my photos for a more active sky. I don’t want it too active for that defeats the mood I’m trying to recall, but I can calm it down. What I find difficult is creating an imaginary sky.
Here is one of my cropped images and my chosen sky. I am working in Canson Moonstone with soft pastels. I hope they will conspire to give me that dreamy, end-of-a-happy-day feeling. This cropping is too severe, I think, but I’m going to start the sky first then ease up to the composition as I see how it goes. What I won’t do is finish the sky before I start on the pergola, and if I like it I may not put the pergola in at all, just find another sky for it! Below is my third attempt!
I have looked at the photo again and have cropped the image a bit wider to include the wisteria (it’s there but it’s a winter photo) and the decorative lamp post. This is Lisbon, so there are all those decorative tiles and some of their decorative pavement. How much of that detail will I show? I don’t know. Certainly the wisteria could grow a bit.
The sky is superb and definitely dreamy. Your task seems very difficult as the pergola would break up this sky. It will be fascinating to see where your artist’s inspiration takes you.
This will be interesting and useful to see, as I’ve found a lot of my photos have almost no sky showing – all bleached out in the printing!