Thank you for reaching out to us again. I'm very sorry to hear about the rejection of your asylum claim.
After the rejection, have you appealed the decision by the BAMF? Have you consulted a lawyer or visited a legal aid service for refugees in your area?
Regarding your first question: I can see that you asked about bringing your fiance before on this thread: I want to marry my fiance and bring her to Germany but I have not received any response from BAMF for my interview. So?
As Thorgen explained in his comments, one of the prerequisites is having a residence title in order to apply for family reunion. Also, you can only apply to reunite with relatives and a spouse or registered partner. Since you do not have a residence title and you two are not married yet, that could pose a problem (still, I'm not a lawyer, so I can't say if it is impossible).
Please have a look at the BAMF website for more details: http://www.bamf.de/EN/Fluechtlingsschutz/FamilienasylFamiliennachzug/familienasyl-familiennachzug-node.html
As for your other question, there may be an option to apply for a so-called "Ausbildungsduldung". The following thread discusses a similar case and explains what the Ausbildungsduldung is:
Is it possible to do Ausbildung with Duldung? Landratsamt didn't give permission
These threads from our platform may also be helpful:
Where can I find an Ausbildung in Germany?
What happens after Ausbildungsduldung and what happens if I quit the Ausbildung?
I would definitely recommend reaching out to a legal aid service/ refugee support or to consult a lawyer in your case. They will be able to have a closer look at your case and inform you about your options!
Feel free to reach out to us again if you need any further assistance. I hope these sources help for now.
All the best,