Grüße, und herzlich willkommen! Ich kann dein Deutsch lesen, aber leider muß ich auf Englisch antworten. Vor 40 Jahren konnte ich es fließend sprechen. Heute nicht. Also dann...
On your audio interface, you need to use Input 1 (INST (Hi-Z)) for your J Bass. You also need to set the switch on the back to Hi-Z (next to the Power button). And then, of course, you need to adjust your inputs SENS so it's almost as loud as you can get without clipping (leave yourself a little headroom). With a bass, especially a passive one, it's helpful to have a compressor pedal between the bass and the audio interface. I have a Markbass Compressore. It's good, but I wouldn't recommend it if you have a pedal board. It's draws a LOT of current and wouldn't play well with the pedal board power supplies I'm familiar with.
I also have a Fender J Bass. They have passive single coil pickups which provide a relatively low output (like when your output drops in half when you split the coils on a humbucker). Active pickups have much higher output, so you have more flexibility there.