this is what I found under my car and I fixed it. I spent 3 months with a welder and replacement panels. If you have never done this before you need help. there is more going on here. Please contact me if you need advise, its a complex job but it can be done and you can be very happy with the results
I did this during covid lock down, it keep me busy and at home.
My car had the same rust in all the same places as yours especially in the boot and wheel arches.