Wolfgang, let me ask you this: Do you have a Z Visa in your passport? If you only have a tourist visa or a business visa then you are putting yourself in a very bad situation. YuMing is a crap company. There is no other way to put it. We all make mistakes, and you've made one if you are choosing to work with YuMing.

If you are a Native English Speaker, then there is no reason why you cannot get another, better job at a public school or university. You need to apply to these types of places, and extend your airplane ticket.