Headlights disappeared after processing at postage

The story: I buy a car near Stuttgart and pay for it. I agree with the seller that he sends the (approved for Japan) headlights to a specialist in Hamburg to prepare and switch to asymmetic light. Both headlights are processed by the company on my bill and sent back to Stuttgart in two packages because of the size. But: During the mail way with the yellow giant back In the meantime, the sender has been able to place an alert at the post office (after 8 days), fortunately both parcels were insured with 250€ each. The paid vehicle is now disassembled in Stuttgart and cannot be assembled and delivered to me. Who has claims against whom here? What about the lost time and the costs that arise because of this? What if, who now replaces both spotlights? Is it possible that someone can consider it more legal than me … Many greetings Thomas PS: Unfortunately, I also hear a Mercedes employee that spare parts are often stolen when they are shipped, if the contents can be identified via the packaging. -That’s gone, he said.