HiFi system for my Audi 80, urgent help!

Moin, first of all praise to the side here, came to it by chance and finds it awesome. Now to my problem, I received the Audi 80 of my grandfather, but it still contains the standard system, I want to have a new one installed. But since I am a newcomer and I have absolutely no idea about it I wanted to ask you here what I have to pay attention to. I have as said no idea of the things I need or about the current Pre I don’t want to install a killer system in my car so that my ears fly away, but only a reasonable system or sound system so that I have good sound and bass, so beginner models are enough for me. So I don’t need the new CD player for the car anymore. The entire system should cost up to 350 euros. Do you have any tips or advice on what in this price range for my Audi a soundwer tig good, and yet inexpensive sound system is? Would you be very grateful for help. Thank you very much!