Welcome
If you do a search on here there is a lot of info on leaks - but the most likely cause of the leak in the back is probably the alpine lights or (if fitted) rear sunroof, and a possible cause of the soggy carpets is either the bottom of the windscreen, or cracks in the floor around where the bulkhead body mounts go on - I had this in mine, just pulled up the carpet, covered it up with silicone sealant and left it at that - too much hassle to repair the cracks so it was easier to fix the leak and forget about it...