I wish I could see it! Where abouts in France are you? (A long shot I know). Regarding all the branches, follow the nice healthy greenery on its branches back to the main trunk to get a sense of what is growing where, do all these branches you have to prop up come from one thick trunk in the ground or are they growing up through the ground separately? That is your starting point - it is entirely possible to cut some branches out, look at your leaf coverage (declining by now I know) and decide what you couldn’t bear to lose and prune, you must have sharp secateurs or loppers if the branches are thicker than a finger and be careful to cut cleanly not tear into a branch, anything that is dark wood - almost black, that snaps like a twig cut it out/off completely. I will take a photo of mine as it is now, and take a photo of my pruned wisteria in January or February and email it to you if you like? You will be shocked at how hard it has been cut back. Basically you can remove as much as you like, but you must keep some branches with buds on growing in the direction you want to keep it. I don’t know the etiquette on here, can you provide email addresses? I am on Facebook if it’s not possible. QVC is a shopping channel of some 25 years in the UK, used to be naff but has really come on. Richard Jackson is a professional gardener from the Geoff Hamilton era, and his products are superb, I stock up when I visit the UK each year (via car) ordering it and getting it sent to my brothers before I arrive, but as I say it is on QVC.fr. Hope this helps?