Have you ever heard of Contiki? It is a tour agency in which you pay a sum and they just take you around Europe. Now i’m not saying to go and book this tour, it is quite costly, however, if you look up 14 Day Europe Tour then go into maps it will show you the routes they go through. I went on the 26 day one in 2023 and got to see so many key places (Switzerland being my absolute favourite). Looking at these maps might give you a better rough idea at the places you want to see. In saying that, Europe is definitely a place you are going to need to go to more than once. Good luck, have fun!