Just to add a little to what Hamid has (correctly) said above: Very often we use 'however' more for it's use 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.")

If we add -ever to wh-words like how, what, we change their meaning. however =‘any way at all’ or ‘it doesn’t matter how’ "However you try to explain it, I still can’t understand it." (Any way at all that you try to explain it … /It doesn’t matter how you try …) whatever = ‘anything at all’ or ‘it doesn’t matter what’ "Please take whatever you want from the fridge if you feel hungry." (anything at all that you want) "Whatever you do, don’t lose this key."