Glad you're enjoying the beginner's course!
As for your question about putting people on a range, yes, that's very tough. Especially if you don't know them at all. However, this is something that you will start to understand more and more as you play more and get more experience.
And no, putting people on a hand is not the same as putting them on a range. Putting people on a range is basically giving them a variety of hands they could have. Putting them on a hand is basically saying "He has AK".
But the thing is, hardly ever will someone have only one specific hand in a specific situation. For example, say somebody check/raises you on this flop:
J
T
2 
If you think he raises here with two pair and sets only, his range will look like this:
JJ-TT, 22, JTs, JTo (assuming he doesn't play J2/T2).
So you can't always say he has JJ here when he raises, for example. Instead, you can say that he has that range of hands.
Hopefully that made sense! If not, just say so. Or, of course, you can always ask Bogdan in the Beginner's Course, as he will be more than happy to answer any such questions you might have 
And of course, although a bit late, welcome to the forum!
Kind regards,
Tino