Do Vietnamese need a transist visa if i have less than 24h and i wanna go out of tranist area?

Hi,
I'm Vietnamese. I will have 14h layover at Beijing (my flight from Paris --> Ho Chi Minh).
If i wanna go out of transit area, is it possible? (To visit Great Wall of China)
Do i need a transit G type? If yes, must i complete before flying or just arrival?

Thank you so much