Mr.Nasr, you can bring yourself following documents to the Chinese Embassy in Qatar.
1. Applicant's passport with blank pages and at least 6 months validity left before expiration.
2. A truly and completely filled application form affixed with one passport-size or 2x2 colored photo,

For a tourist applicant, in principle he shall evidence his financial capability of covering the travelling expenses in China, and when necessary, provide the air, train or ship tickets to the heading country/region after leaving China. For the applicants who come to China to visit relatives, some are required to provide invitation letters from their relatives in China.
Other documents required by the visa officers if necessary.

Visa L is characterized by a short duration of stay, usually 30 days, no more than 90 days, and could not be extended upon expiration. Besides, you can not get a visa on arrival. So, better to apply for one before your departure.