Many asylum seekers believe they will have better chances in their asylum process if they work, but that is not true. Whether you will be granted protection in Germany has to do with what you have gone through in your home country. The Federal Office for Migration and Refugees (BAMF) is not interested in whether you work in Germany or not or your level of fluency in the German language.
German proficiency, however, can help you -regardless of the result of your asylum procedure - to stay in Germany: rejected asylum seekers or people with a tolerated stay (“Duldung“) can, for instance, obtain a so-called Tolerated Stay for the Purpose of Vocational Training (“Ausbildungsduldung“) if they start a qualified vocational training ("qualifizierte Ausbildung"). An “Ausbildungsduldung“ allows you to stay in Germany for the entire time of your training programme. If you find a job in your learned profession after completing your training, you will be granted a residence permit for another two years. This is called "3 + 2" regulation ("3+2" Regelung).
So it pays to learn German as soon as possible after you arrive in Germany and start vocational training. Then you can apply for a Tolerated Stay for the Purpose of Vocational Training ("Ausbildungsduldung") in case your asylum application is rejected. If your application for asylum has already been denied or you have never applied for asylum, and you currently hold a "Duldung", it may be worth your while to apply for vocational training.