You got it. It's just an embassy, and it's our embassy. Germany has no say in this. In a way, it's a plus for the Palestinians. They want Jerusalem as their capital of a Palestinian state. So Trump caters to both by moving our embassy there, to handle stuff for the two states. Easy.
The larger picture is that the peace process has gone no where for 22 years since the law was passed to move our embassy to Jerusalem. So President Trump created a bargaining chip for himself by saying he'll move the embassy, and can trade that off in exchange for something big in any new peace discussions. This will provide a reason for the Palestinians to get off their butts and actually discuss peace. Which of course they don't really want, but we all know that. When the talks fail (again), we will have our embassy in Jerusalem, where it belongs.
Nicely stated.