unfortunately, this will not be an easy task. Since you are entitled to subsidiary protection, your claim to spousal reunification is quite difficult. You would have to be married in the first place.
In order to marry your fiancée here in Germany, she must come to Germany. Only then can you marry her in front of a German registry office with the necessary documents. You can apply for a so called wedding visa at the German embassy in Beirut. You will need some documents, your fiancée has to proof her German language skills at A1 level and it will take some time.
Alternatively, you would have to marry in Syria, which of course is not possible for you.
However, you can also marry legally in Syria by proxy. See our previous article (German):
The following steps are required:
You would have to draft a letter of proxy in German, which must contain the exact details of the concerned parties (name, place of birth, date of birth, place of residence) and the exact act of the proxy (marriage by proxy).
The letter of proxy must then be translated into Arabic, verified by a notary, and certified by the district court located in the district of the notary.
Additionally, the Federal Office of Administration in Cologne must then certify the proxy.
Finally, it needs to be certified by the Syrian embassy/consulate, for which you as the principal would have to appear personally.
Only after completing all these steps and after the Syrian Embassy certifies the proxy, will it be recognized by the authorities in Syria. I.e. only then can a relative of yours legally contract a marriage by proxy for you in Syria. Afterwards, it must be recorded in the Syrian register of marriages.
Subsequently, Spousal reunification would be possible in principle. However, it is required that the wife, who is still in Syria, has German language skills on the level of A1. An application in accordance with Section 30 of the Residence Act must be submitted to the German Embassy in Beirut.
Hence, there are many obstacles to overcome and it will certainly take some time.
Here is the link to the German article (Link zum deutschen Artikel).