Very often we use 'however' more for it's used as a signal to the listener or reader than for it's actual meaning. It is used to connect two ideas which are opposing. A bit like the word 'but'. For example, "Venice is a very beautiful tourist destination, however it is too crowded."

We often use 'whatever' to emphasise feelings in two ways. Firstly, in sentences like "What are you doing?" or "What time do you call this?", where using whatever (Whatever are you doing?/Whatever time do you call this?) expresses surprise, confusion or indignation. Secondly, 'whatever' is used as exclamation signifying indifference - for example "Hurry up or you will be late for work." "Whatever." (meaning "I don't care if I am late for work.")

From: https://www.italki.com/question/423506