Question

It isn't a standard idiom if that is what you mean.

I suppose if I like a casual lifestyle then it would mean that I avoid formality and too many rules and regulations, like to be relaxed, dress in a casual way etc (and I do!)

Everyday life means what happens on a routine basis, this is not necessarily casual. The Queen's everyday life is probably a lot less casual that mine

Actually, it's from a composition of a student of mine. She is supposed to write something like "The reason why native people there invite you is that they would like you to know their lifestyle at home better."

Is it possible to replace "their lifestyle at home" with "their casual life"? If it's not, then why not? I myself think it's not, but I don't know how I should explai

Becasue, as I said, their home life may not necessarily be that casual.

'home-life' covers the meaning adequately for this context.

OK. What about the expression "casual life" itself? Although, as you said, it is not a standard idiom, does it make sense at all? If it does, what could it be?

It doesn't really make too much sense to me as a phrase on its own, no, other than as a casual lifestyle as I said in my first answer.

Someone else may have another opinion though?

It doesn't really make too much sense to me as a phrase on its own, no, other than as a casual lifestyle as I said in my first answer.