hello

im a swiss citizan and i have a 6month(valid till 7of july) double entry L visa for china with 30days at each entry.im in hanoi right now and want to go back to china the 24th of mai.ill leave china the 7of july..so that means i want to stay longer than 30 days in china...is it possible to apply for a visaextension in china after my 30 days expire or can i get a visaextension at the chinese embassy in hanoi before entering china?thank you for your help.best regards