Mini-job in a bakery?

Hello

I'm currently finishing my Abitur, so I'm still at the beginning of my EF (university entrance qualification) and would like to do a part-time job at Malzers or Gatenbröcker or something similar. My question is, does anyone have experience and can tell me what it's like and what the application process is like? Do I just apply online, or do I have to find a job posting first?

I have no real professional experience so don't be surprised

thanks in advance