How to find an object (house/apartment/land) nationwide in Germany?

Hello everyone!

My situation:
I, married, no children, will work for another 2 years and then retire from working life at 57.
I currently live in Cologne, but only because I also work here; nothing really holds me here, so to speak, the (German-speaking) world is open to me for my (pre-)retirement time.
I haven’t owned a car for over 20 years, and that is how it should remain.

Expected finances in 2 years:

[*]Assets: approximately 700,000€
[*]passive income: 3,000€ net/month
[*]current expenses: 1,800€/month (including 800€ warm rent), meaning if I simply stayed in my current rented apartment I would save 1,200€ every month.

What I am now looking for is a place where I can live for the rest of my life that meets the following conditions:

[*]quiet. VERY quiet!
[*]shopping facilities for daily needs within walking distance. As mentioned, no car!
[*]around 100sqm living space. A garden is not necessary, but possible.
[*]senior-friendly. Not necessary yet, but will certainly be needed at some point.
[*]it can definitely be an apartment instead of a house, as long as I hear little to nothing from the neighbors (I know this is very hard to estimate).
[*]not sure if this still needs to be mentioned nowadays, but reasonably fast internet is also a must
[*]preferred would be a place either directly on the water or in the mountains

Very roughly estimated, this means for me I can either

[*]rent something for up to 2,000€ warm/month => I would remain roughly at break-even at the end of the month and would not touch my assets at all
[*]buy/build something for a total price (including moving/new furniture and all costs that go toward the property itself) of 600,000€. I definitely want to keep 100,000€ as a reserve.

Since I myself am car-free, my first thoughts go to places that are car-free themselves, e.g. some of the German islands (I am not afraid of island madness).
But a penthouse apartment or even just a quiet location would also fit.

My questions about this:

[*]How do I find something like this? The problem with real estate websites is that the search almost always starts with entering a postal code. But I am flexible right now and can hardly sift through all postal codes one by one. Agents are generally also rather local.
[*]When does one start the search seriously? From now on, the earliest time to move is in a little less than 2 years, but there is also nothing against staying longer in the current rented apartment if circumstances require it.

Thank you!

What about contact with the children? Where do they live? Wouldn't it be nice if the grandchildren quickly visited by bike to tune it up or paint the fence together, etc.?

There are no children. Other relatives live in Duisburg (where I also grew up), but I am not necessarily drawn back there either.

Enter "Germany" as the location and navigate through the filters and, if applicable, your own search criteria such as "Seeblick", "Meerblick" or similar to approach the suggestions, for example using the map view. I just tried it on a leading blue/orange portal, it works.

Oh, sorry, I misread that. If I were that unattached, I would specifically look for a natural paradise, with a hospital and nursing staff nearby. Polish border? Sorry, but you have to be honest. The older you get, the more often you visit the doctor and the more help you need.

There is also the possibility to post such wanted ads on these real estate websites or on classified ad sites with 4 letters. There you can then list your wishes in detail (as done here) and the agents, landlords, sellers, etc. will contact you themselves and offer something. However, I do not know how this is actually used, as most people tend to take the reverse approach. I only know that these options exist. Under such financial conditions, good offers should come in there.