How do customs work?

Hello, I'm wondering how customs in Germany works. I have sent a car part, specifically a throttle body to Germany from Norway. When it first arrived to Germany, Frankfurt it was stuck in customs for 10 days before it moved on to the final destination. I have asked the company which were gonna repair my throttle body if they have recieved it. They told that they know the part is in the area but they get notification by mail, not email. And they have to wait for a processing number and explain the customs how they should proceed. What does this actually mean? I'm kinda stressed because according to my tracking the deadline for pickup is 9th of July. Thank you for answers.