First, you need to prepare the required documents listed on China Business Visa(https://www.travelchinaguide.com/embassy/visa/business.htm), then submit the visa application to China embassy/consulate in Germany which covers the consular jurisdiction over your residence. Mailed application is not accepted, no appointment is required. If your application is accepted, you will be given a receipt, on or after the pick-up date specified in the receipt, you can pay and pick up your visas in person or by entrusted persons, travel agencies with the receipt. The stay duration is up to your demand and decision of the visa officer. After you get a F visa to China, you can apply for extension at the local exit & enter department before the expiration of your visa.