I once wrote a letter to a German club and received a reply. The format I wrote at that time was based on the ordinary English letter format. If you are a student, your teacher must have taught you how to write English letters.
But I suggest that the content of the letter can be changed to German. If you don't know German, I'll teach you a way. You can find a German on MSN or ICQ, and then you can write a letter in English and send it to him, so that he can help you translate it into German and return it to you. This will be a complete German letter. That's what I did at that time, and it worked well. It's as if I wrote it in German myself. Moreover, because it is translated by Germans, there is no language disorder, which makes it very friendly and convenient for Germans to read. If you use turtle mouth English or simple Chinese that foreigners can't understand, I don't think the other party will reply to you.
As for what you want to write, you can first introduce your origin and your fan experience in a paragraph. After that, you can say whatever you want, such as summarizing Bayern's situation in China and how you became a Bayern fan. You can also talk about the situation of Bayern in recent years. At the same time, you can also give some suggestions, such as what players to buy in winter and how to adjust the lineup, which will make people feel that you are not an impostor, but a veteran or at least an enthusiastic Bayern fan. Finally, you must express that you will always support the team, which star in the team you like best, and so on.
Don't write too long letters. Make it ten pages and eight pages. No one will read it. People are busy. One or two pages is enough, and the paper should be better. Don't make a school stationery or paste some snot on it. . .
As for stamps and envelopes, don't worry. When you go to the post office, people will calculate the price of stamps according to where you send letters. I remember that I spent about 6 yuan on stamps for 7 yuan, using international stamps. Envelopes also have rules. For an international envelope, it is probably 1 to 2 yuan. The format of the envelope cover is also stipulated. You can ask the post office staff about this. Now I have forgotten the format.
Be sure to write the address in English, not Chinese. Don't worry, the postman in China can read it. . . .
It is only about 20 days from the time I sent this letter to the time I received it, which is quite fast.