Hi,Des
It seems that you are visiting just one place in one city, WOW in Shenzhen, House of Barbie in Shanghai and Great Wall of China in Beijing. Why not spend more time on other places of interest?
Where are you now? In shenzhen or in Philippines? Actually, it doesn't matter which one comes first, you just use flight to transfer between Shenzhen and Shanghai, Shanghai and Beijing. Say if you are starting from Shenzhen, take flight from Shenzhen to Shanghai and then use Shanghai Subway to get to House of Barbie.
And then take train or flight from Shanghai to Beijing. Take this site for the transportation between the airport and Badaling Great Wall: https://www.travelchinaguide.com/cityguides/beijing/greatwall.htm
Wish you a nice trip in China!