Frankfurt - Amsterdam - Shanghai - Sanya

How long will you stay in Sanya and what's your next destination after Sanya?

As you have 2 stops, your transit time in China is limited to 24 hours.
When you wanna stay longer in Sanya, you need a visa.

But as long as I don't know your complete schedule, I can't give you a proper answer.

You need to apply for a tourist L visa before your trip. Multiple Chinese landings limited to the 24 hour direct transit. Since you arrive in Shanghai at 10am you must leave Sanya for third country by 10am the next day. You are already way over

Do not try to trick immigration with a ticket for a flight you won't be taking. They will find out and you will be arrested.

Assuming you want to visit Sanya, visa-free visit is only available to those clearing immigration at Sanya Airport (i.e., arriving directly on an international flight). You are obviously not and hence need a visa.

It's Chris writting. Thank you all for your helpful information. Given the fact that our flights are already in 2 days we changed our flights and are now flying into Sanya via HongKong for beeing able to participate in the visa free entry.

If you are departing to Sanya directly from Hong Kong, you can rely on Hainan visa on arrival. If you are a citizen of Netherlands, the price of this visa will be 168 CNY upon your arrival in Sanya. Very good detail about Hainan visa on arrival is that you are allowed to travel from Hainan to one of mainland Chinese destination and explore it before you depart back to Europe. In other words, when traveling on Hainan visa on arrival, your itinerary can look like:

Amsterdam - Hong Kong - Sanya - Beijing - Amsterdam

All the above mentioned is covered by Hainan visa on arrival.

Just to be clear for other readers, Hainan visa on arrival is safe only if you are departing to Hainan from Hong Kong and maybe from Macau. Any other airport beside two mentioned, will not allow you to board the plane.