Sounds like a wiring issue or dodgy earth. I'd recommend a diagnostic check to see if any fault codes flag up or get an auto electrician to take a look.
I'd recommend checking the wiring but I'd bet it's an issue with the radio itself. Cheapest option would be to replace the head unit with. Second hand one from eBay. You'll need the radio code for the replacement unit.
Have a look at buyers guides on YouTube.
Make sure heater is working and consistent, if it's not it could be a blocked heater matrix.
If you're looking at autos make sure the gearbox has been serviced on time.
The subframes are becoming a common rust problem on older audis. I'd recommend you get someone wire brush the rust to establish how bad it is then if it's ok, paint the bare metal with paint etc.
Remove gently the cap from the back eof the nozzle is just slid inside, easy to remove with a Plier they are cheap in Amazon or similar.
When you reinstall you can use a pick to adjust the stream so it lands perfectly ahead of the wiper.
Welcome to the forum you'll find the members on here are a friendly and helpful bunch 🙂 bag group do like to over complicate electrics and computers for sure.
Definitely get matching springs and shocks or at least matching size. Definitely don't cut the corner of just the shorter springs and standard shocks. Obviously the other option is coilovers but that'll make the ride firmer.