Translation:Four boys sleep on this big brown bed.
I think "in this big brown bed" could be accepted.
To answer the rest of your question: if I haven't gotten up yet, I would say "ágyban".
And when people go to bed, "ágyba bújnak/fekszenek". And breakfast in bed is also something that happens "ágyban".
But you can lie down on a bed, correct? Just like in Hungarian.
I think it has to do with the "normal" night activity and related actions. Those are referred to as "in bed", "ágyban", etc.
But if you just casually lie down, that is more like "on" the bed, "ágyra", "ágyon".
Ok, it sounds fairly similar between English and Hungarian.
Lying on a bed makes perfect sense. Sleeping on a bed -- I think I'd usually say sleeping in a bed instead. Maybe it's the same in Hungarian? Does the original sentence sound a little bit funny?
I think I'll in any case refrain from making a report on this one.
I think it is the same in Hungarian.
But usually four boys do not sleep in one bed. Must have been a party with a sleep-over. So you see the bed and notice "hey, there are four boys sleeping on this bed".
Also, there is one more thing: when talking generally about who sleeps where, we may tend to use "ágyon" more frequently.
"Te ezen az ágyon alszol, én pedig azon." - Basically, this is your bed and that one is mine.
But when we actually go to bed, we are "ágyban".
But "ágyON" is by no means mandatory to use. It is just an extra option.
That is also an existing formula. There is a discussion about it somewhere in this course. For example, you could say:
"E nagy barna ágyon négy fiú alszik."
What is interesting is that this much simpler version is much less used than the complicated one. (It is mostly used in more formal, official texts.) So you are better off learning the complicated formula because that is what you will encounter most of the time.
Btw, note that this simple form is only used in a "this"/"these" situation, not with "that"/"those".
You are very welcome.
A good thing about this "e" formula is that it is very simple. You just put the "e" where "ez a(z)" would be, and you can forget about it. There will be no suffixes or postpositions added to it.
But, again, this formula is not widely used, and there is more (or less) to it than I can explain here.
But let me add that it can come in the forms "e" and "ez". And what I said about the "a" version is not exactly correct. There is a very limited use of the "a"/"as" versions as well.
And then we can add that there are further variations: "eme", "ama", "ezen", "azon". They are used similarly, with no suffix or postposition added.
Anyway, really, try not to use this formula, until you are quite familiar with the language and its usage. It is very easy to get confused over the various, very similar but different, formulas.
Here are a few typical usages:
"e napon" - "ezen a napon" - on this day
"e házban lakott ..." - "ebben a házban lakott ..." - "... lived in this house"
"ez alkalomból" - "ebből az alkalomból" - on this occasion
"e/ezen útlevél tulajdonosa ..." - the owner of this passport ...
I tried to find some previous discussions on this topic, here is the only one I found:
And there is a loooooong discussion on this and that, here: