This itinerary doesn't include any travel time which will you would need an awful lot of if you plan to stay such a short time in each place. You have eight cities listed but only 22 days. Is there a special reason why you have picked Hamburg to visit? I would not think it would be a top choice for a first visit to Europe. What do the other people you will be traveling with want to do? What are your main interests? How do you plan to travel from place to place? What are the top places that everyone in the group wish to visit?

If you have 22 days, I would limit the trip to 5 places at the most. I put an extra day on location #4 as you'll be dragging by then. Here is a possible template:

Day 1 arrive and get over jet lag. Your first day is usually spent in a blur.
Day 2, 3, 4 sightsee in location #1
Day 5 travel to new location
Day 6, 7, 8 sightsee in location #2
Day 9 travel to new location
Day 10, 11, 12 sightsee in location #3
Day 13 travel to new location
Day 14, 15, 16, 17 sightsee in location #4
Day 18 travel to new location
Day 19, 20, 21 Sightsee in location #5.
Day 22 Fly home from location #5

You must have a great budget to work with considering the hotels on your AI planned itinerary. I had considered staying at the Hassler last July for a meeting and the rooms started at $1600. My partner and I have high incomes but we don’t want to spend that much on a hotel room. The Bristol in Paris is even more expensive at over $2000 a night. You better have at least $100,000 for 2 months for two people to travel in this style.

Take the Kontiki tour. I'm not sure you'll be able to understanding the logistics to plan this trip on your own.

They are four 50 tear olds -- Kontiki might not be the best option . . . :)

Just to be contrary to the "it can't be done", I once (a very long time ago) took a five week trip that was one week in England, one week Netherlands/Germany/Austria, two weeks Italy (and I think it deserves the most time) and one week France (well, really just Paris). Then we returned to London to fly home. We were young and poor so took a couple night trains (which I would not recommend unless you can sleep anywhere) and skipped Switzerland because of the cost. It was a good trip, all taken by train, and I think we saw quite a bit. I have been back to Europe nearly two dozen times for more in depth visits to these and other countries in the four(!) decades since. If you have eight weeks instead of three, you could add time to the Benelux or France, or even Scandi (Denmark or Sweden probably are your best bets), or Spain, or somewhere in Eastern Europe (although for a first trip I would recommend skipping those counties and going no farther east than Austria).

I don't think you should take a tour. Those waste a lot of time "rounding up the troops", and you end up with silly shopping stops and places you don't want to go. Get a Eurail map and mark out where you want to go. Sometimes flying makes more sense than taking the train, but you miss scenery.

Good luck.

Well, "anything" is possible if it's checking places/countries off a list but not actually sightseeing. This trip is 20 countries in 31 days...

Jean, the OP clarified in Post # 20 that they have up to 8 weeks.

Nevertheless, the OP has not been back since 1/21 acknowledging their AI attempt was too much. I think we need to allow the OP and their travel companions time to digest our responses and, hopefully, research.