So now I finally dicided to finish and publish my fantastic experiences of work-exchange programmes in Germany. Please forgive me if I made some grammatical errors in this article, maybe I spoke too much German now so my English became worse...
The are many platforms available for people who wants to join the work-exchange programme worldwide. The one I choosen called "Workaway" (https://www.workaway.info/). In order to reach the host, you need to pay and became a member first. The way to find a host is quite simple, just go to the "host list" and select the country and region, then you could see the description of each host, as a member you could sent message directly to the host and ask if they are able to host you. I consider myself quite fortune cuz the hosts I'v met were really super nice, but I've heard some not so good rumours from other "workawayers" (the peope who participated in workaway) about their previous host. So to avoid some unpleasent experience, it is suggested to look up to the host's profile page carefully, and maybe have some chats with the host first to know each other better.
Following are my two great Workaway experiences in Germany: