Nice to hear from you again.
It's true that just filing an appeal is not sufficient to be successful with it. You (or even better: a lawyer) has to explain why you appeal against BAMFs initial decision. That's why they rejected your appeal so quickly.
But there are a few options left that allow you to stay that you should think about:
1) Try getting an Ausbildung. This way you can apply for a so-called "Ausbildungsduldung" at Ausländerbehörde which allows you to stay for the duration of your Ausbildung (~3 years) and the following two years if you find a job afterwards.
2) You can hand in a so-called "Asylfolgeantrag" which is like a second application for asylum. But keep in mind that it is only going to be successful if you can provide fresh evidence that hasn't been taken into account during your first procedure. For example, if the situation in your home country changed for the worse so that you are now facing a danger of life or persecution if you would return. You should consult a lawyer for this.
3) This one is quite drastic and I just mention it to show you all options that come to my mind right now: If your girlfriend is German/a EU citizen you can try to get married. This way you have a right to get a residence permit. But it's quite tricky to marry in Germany as a rejected asylum seeker. If you need more information about this topic, check out the article on the Wefugees blog about it: https://wefugees.wordpress.com/2018/04/20/heiraten-in-deutschland-how-to-marry/
Unfortunately, you are not present in Germany long enough to be eligible for a residence permit based on being well integrated into the German society. That's only possible after 6-8 years