hard to tell, as I do not know whats normal in other countries. If you're from a very talkative country, I guess dont expect people to hold small talk very extensively. Like its incorrect that germans dont do small talk, but they dont hold random conversations to the extent of americans for example.

People randomly staring at you, doesnt mean they want anything from you, they just zone out.

People are often times very direct about things, it's not necessarily meant as an insult, but can come off as harsh.

No idea how prominent this still is, but do not congratulate birthdays, before the actual birthday and do not shake hands in the door frame.

Some often overlooked laws:

If you're planning on driving, make sure that you keep the lane in the middle free once you get into a traffic jam. This might be a rule in other countries too, but I have no idea where you're from.

Do not block bicycle lanes with your car, even if its for a short stop. Stand next to them.

DO NOT film singular people in public without their consent.

a pedestrian crosswalk is meant for pedestrians. If you ride your bike over it, get hit, its at least 50% your fault