Firstly, I want to thank to all contributors to this forum and all answers to my questions which were greatly appreciated.
I'd like to share some thoughts with fellow travellers who might find this trip report interesting.
Generally speaking, Canada is a safe country with good tourist infrastructure - a network of tourist offices, clean public toilets (restrooms or wash rooms) and easy communication in English. Canadians are laid-back and helpful in some cases. They adhere to rules and expect them from visitors.
Some remarks about the visited places:
Toronto - like New York. A big sprawling city with traffic jams, rather boring city. Easy orientation, a lot of homeless people. Most attractions (CN Tower, Ripley Aquarium) have exorbitant prices. A ferry to Toronto Islands is highly recommended. Scarce public transport (transit) and quite expensive. I'd recommend two days plus one day for an easy DIY trip to Niagara Falls. All other national parks are too far from Toronto and require about 3 - 4 hours of driving
Niagara Falls - doable in one day. Worth a visit, however not a big natural wonder and an over-matured theme park.
Montreal - a city with European charm. A walk to Mount Royal is enjoyable. English is not spoken here but not a problem in tourist places (there are usually signs in English). The Montrealiens are definitely friendlier and more helpful than people in Ontario. Accommodation is cheaper than in other parts of Canada. Maximum two days.
Quebec City - worth a visit even for visitors from Europe. It reminds cities in southern France. The city centre is easily walkable. As this city is overcrowded by visitors, prices in the tourist area are really high and don't match the quality. Maximum 1,5 days.
Charlottetown is a sleepy small city with its relaxing atmosphere. Not many sights (the founding birth place of Canada is closed). But worth a visit. The Confederation Trail is beautiful, hire a bike. Maximum 1,5 days-
Halifax - a city with few sights but the Citadel is one of the most important sights in Canada. A good starting point to Lunenburg and Peggy Cove (both sites are on an UNESCO list together with national parks in Western Canada and Quebec City). A ferry to Dartmouth with a cheap price offers a great panorama view of Halifax. Maximum 2 days.
There are some negative points:
Canadian eTA is mandatory for most travellers to Canada. The process isn't user-friendly and straightforward. You have to do in one step and pay immediately otherwise you start from the beginning. US ESTA is better managed.
Immigration and arrival in Toronto Pearson Airport: Canada border agents are very unfriendly and rude. Canada is NOT open to foreign visitors. They are suspicious and require to show reservations, money, credit cards etc. Even if you have a Canadian eTA, you have to fill a custom declaration in paper. They use a red pen to make remarks in your custom declaration and send you to additional counter for extensive check. Have all documents handy and in a paper form. They don't like electronic versions. The airport is shabby with long badly signposted corridors. The personnel is rude and shout at visitors Limited public toilets. Luggage was delivered after 1 hour after the plane disembarkation. Plan at least two hours from the plane to the airport leaving.
Flights in Canada are some of the most expensive in the world. If want to fly within Canada, increase your budget significantly.
Canada is one of the most expensive countries on Earth. Plan your budget accordingly. They don't expect visitors on a tight budget. Tourist offices are aimed at wealthy tourists and reluctant to help tourist on a tight budget.
The season in Canada is shorter than in other countries (the most outdoor attractions are open from late May until the beginning of October). It‘s valid for accommodation as well.
The public transport is almost non-existent with an exception for Toronto and Montreal. If exists, exorbitant expensive.
Renting a car is really expensive in Canada, particularly if you travel between regions. Plus expensive fuel.
Public services are poor and the competition is limited.
Canada is a vast country. Incorporate long distances between places / cities in Canada into your planning and plan realistic times.
Higher taxes than in the US are prices are shown before taxes. In some cases you have to add taxes about 20 %.particularly for accommodation. Always check the final price with your accommodation provider to avoid any bad surprises.
The US offer a better value-for-price ratio than Canada.
Think TWICE before going to Canada.
Thank you for reading my trip report.