I didn’t much like Marienplatz, very crowded, but the Deutches Museum, Alte Pinotek and Englischer Garden are excellent. At BMW go to BMW World as well as the museum. It’s a huge showroom of cars and motor bikes. It is across the street from the museum. I don’t know if it is open on Sundays, you can check. There is no reason at all to avoid public transport in Munich, it is very good. The airport is some distance from the city and I think not many attractions there. I am staying at the Hilton next month which is right at the airport, just in transit, not planning to visit the city.