The Chancellor (now Scholz and before that Merkel) are the heads of government and are, in practice, more influential. Technically the president (“Bundespräsident”), which is the head of state, stands above the Chancellor and so does the president of parliament (“Bundestagspräsident”). But this is mostly a ceremonial hierarchy and while the president has to “check” laws and sign them to take effect, this is basically always happening. In general the president is mostly a ceremonial position.
You hear a lot more about the chancellor, because as head of government, they are the only ones actually involved in creating/changing laws (of the positions mentioned).
Edit: If my research is correct, it only happened 8 times since 1949 that a president did not sign a law that was accepted by parliament and the last time was 2006. So it really is a pretty rare occurrence.
There will plenty of options for him to get his puppets in power in Europe too. But until then we really should tell him “stfu” as often as possible and as loudly as possible. And then we hope he has a fallout with Trump rather sooner than later, so he has to focus more on staying president in the US and has less time trying to meddle in our affairs here…