B Corsa Sound System

Hello community, it’s about a little B Corsa, I bought it last year total newcomer etc… I didn’t know therefore that you can shoot the boxes with the volume knob. I’ve been scratching bass for 3 weeks at the back right. I took off the clothing for a while on the left side and the rubber was already pouring out of the box. My buddy recommended me because I want to have sounded a little more pleasant. that I put in front 2 new ones and clamp down the back and 2 new ones should be built into the hat rack. and the amplifier or whatever screw on the back of the backrest from the rear seat. Now I don’t really have any idea of the equipment. (Cables are all already installed there was probably already something installed. (plus pole to the battery with fuse, mass cable attached to the carroserie, remote cable goes up to the radio and hangs out under the glove compartment. My car radio is one of JVC with Bluetooth. it has cost new approx. 100€. I don’t know the exact name anymore. Now I wanted to know what I actually need everything. At the front I don’t want to be a DB Crank or anything else. just want to turn on good sound and sometimes a little louder