I'd like to know how to get a Chinese visa, how to extend it and how to get a LONG-term one.

Alex, to apply for a mainland entry permit, you should firstly prepare all the necessary documents, and then go to the CVASC office to submit the application. The documents required for different types are different. After you enter, before the entry permit expires, you can go to the local exit and entry administrative bureau to extend it. The application process for long-term one are the same as that for short-term one, but more documents will be required and the approval process is more strict.

It takes six business days for processing the application. The fee is 71 francs for a single-entry type if you are French.