الجواب وباللہ التوفیق

As per the situation described in your question, it is difficult to understand that due to the beard you are unable to apply the mask properly. As there are many physicians with beards, who are currently using different types of masks (some bigger than others) which cover the nose, mouth and beard as well as fulfill the requirements from the hospitals they are working for. Based on our own experience as well, we do not see such difficulty in wearing the mask properly.

We recommend that you find such a mask which fits your nose mouth and beard, some of which we are using currently as well. 

واللہ اعلم بالصواب