Denmark - Guangzhou - Hangzhou - Denmark

There is no such thing as a 72 hour Visa. It's a transit without Visa but you are not in transit but doing a trip to China. You need a visa

Unfortunately, you are not eligible for any kind of visa free transit scheme because your itinerary has two consecutive stops within mainland China and your entire stay within China will exceed 24 hours. Also, you cannot travel from one country to China and return to that same country. One more detail. There are no direct flight connections between Denmark and both Guangzhou and Hangzhou.

If you wish to be eligible, your itinerary will have to look something like this:

Denmark - some other country - Guangzhou - Hong Kong

You can reach Hong Kong from Guangzhou by plane, ferry or train, but you will need this ticket before your departure to Guangzhou.

Hong Kong - Hangzhou - some other country - Denmark

So, if you really want to travel using visa free transit, you will have to adapt your itinerary to the rules of visa free transit in the way as I have mentioned you.

Of course, if you want to bypass the hassles of planning visa free transit itineraries, you can obtain a Chinese visa in advance. Now, it's up to you to calculate which one of the options will be more convenient for you in every sense.

Of course, you can fly directly from Shanghai to Denmark. This will be probably more convenient that flying from Hangzhou to Denmark via some other country.

Thank you very much.
So my itinerary can look like:
Plane from Denmark 19/11 with stop in Amsterdam and then land in Guangzhou 20/11 where I stay the day and then go to Hong Kong where I will fly to Hangzhou also on the 20/11. I will stay in Hangzhou 21/11 and go to from Hangzhou to Shanghai airport on the 22/11 and from Shanghai to Denmark also on the 22/11.

Yes, you can do exactly as you have written.

Your first itinerary will be:

Amsterdam - Guangzhou - Hong Kong

This one will be covered by 24 hour visa free transit because you will stay there for less than 24 hours. Now, you can choose whether you will use a train or a ferry to reach Hong Kong. For example, you can take a metro, Line 4, from the center of Guangzhou to Nansha Passenger Port station from where you can take a ferry to both the center of Hong Kong or directly to the airport (Skypier at HKIA). Please, keep in mind that you will have to book a ferry ticket online in advance. After a booking, you will receive an e-confirmation that you will print out and take with you. This printout will be your proof that you will be really in the transit. Also, you will have to take exactly that ferry that you have bought your tickets for. You will book your ticket through CKS - Chu Kong Passenger transport company website.

Your second itinerary is:

Hong Kong - Hangzhou - Shanghai - Denmark

Here you will enjoy 144 hour visa free transit because your stay within Shanghai transit zone will be longer than 24 hours. You are perfectly allowed to arrive to Hangzhou and depart from Shanghai. Probably the best option to reach Pudong airport in Shanghai from Hangzhou is to take a direct bus departing from two Hangzhou bus stations direct to Pudong airport. The ride takes about 3 hours, so you have to plan accordingly. Of course, you can take a high speed train to Shanghai Hongqiao station and from there take a metro to Pudong airport.