Yeah, sorry mate. It's a tough one. I assume the process is the same with customs in any country, but there's a business for it in Germany.
You gotta declare the goods with a customs code (HS code). If the sender doesn't do it, then you can do it manually, or the carrier can do it on your behalf (and charge you for it). Declaring it manually is hard to find, and the carrier never makes it easy for you to do it (because they make money from it). DHL will do a number of line items for free, then start charging you.
The line items are the total number of different HS codes AFAIK. So if you have a lot of items in different categories, then it adds up. Ie. only resistors would be a single line item.
Solutions:
- Find a supplier who declares on your behalf. I only use Tayda for pots now, for this exact reason. LCSC for everything else.
- Self declare before you accept DHL to do it for you (read the fine print).
- Pay DHL.
In the current case, you are importing goods from outside the country and DHL is helping you to get it through customs.