welcome to our community and thank you for sharing your question with us.
First of all congrats to the pregnancy!
Now to your questions:
It all depends on the type of visa and contract you have. In general if you have entered Germany with a working visa and you are already employed, then the pregnancy is not a big deal, as you can still wotk for now and do your Anpassungslehrgang without disruption. However, once you are not able anymore to work due to your pregnancy, it might effect the contract etc, but here it is important to know with what type of visa you are stying in Germany at the moment.
In the first place if not yet happened please seee a doctor, in order to obtain the Mutterpass- a book that you get from the gynogologist and that certifies at what stage of pregnancy you are in and the health of the baby is documented there. This will be your proof of pregnancy for all the adminstration offices involved( now and in the future). In regards of the father: it is as long not important where he is, as long you do not want to bring him to Germany.
I hope I was able to guide you in the right direction if you have further questions, please do not hesitate to use our platform.