Czech Benoni game

So I was playing a Czech Benoni game online as Black, following the instructions of this opening module in month 1. The game went 1. d4 Nf6 2. c4 c5 3 d5 e5 4. Nc3 d6
and now instead of playing 5. e4, my opponent played Bg5 instead. This is the first time I'm playing this system but Bg5 seems to make it easier for black to trade off white's dark square bishop, which white shouldn't do, according to the opening module. Well, anyway, so I continued with Be7 and now my opponent played Bxf6 and I took back the bishop with Bxf6.
Now at this point, a fairly strong player (1900+) came over and made a comment on the game, saying that I'm in a terrible position, with a bad bishop and very little space. Okay, so according to the opening module, Black should try to trade off his dark square bishop, I didn't do that cause my opponent took the knight instead, but I'm thinking that my opponent just lost his good bishop and I can always try to trade my bad bishop for a knight or maybe focus on attacking the dark squares. So I don't really think this position is very bad for Black at all, and I was a bit ticked off with the person said this is a terrible position for me. What do you guys think? Would you have played something else besides 5...Be7?

I don't see what the problem is. Black is doing just fine. The key is to take advantage of the trade and open up the position. It will only benefit white if he can keep the position closed.
If white played e4 on the next move, then I would play the Bishop back to e7 and follow up with 0-0 and f5.

yea I think you're right, Black should open up the position and should be good, although I'm not sure about playing Be7 on the very next move, seems to be violating the opening principles I think I would rather develop some of my pieces first before doing that, but Be7 f5 is a good plan

Be7 is justified by White making a mistake with Bxf6. I checked my analysis with Fritz 10 and the machine agreed with my suggestion, assuming white actually played e4 on the next move. The point is the queenside can wait a few extra moves in order to get your house under control. You could play 0-0 before Be7 if you like, but those should be your next 2 moves (again - only if white played e4).
Good luck with the Benoni. I personally dont like playing those type of positions, so I never play it. I found the Dutch to be much more flexible against 1.d4.

I've only got seven games in my Master Games DB with 5...Be7, but black won six and lost only one, so it can't be that bad. I ran an opening report in Chessbase master DB and Bg5 scores only 17% for white - it's a real dud.

Only one game played 6.Bxf6,Bxf6. The Black dark square Bishop had a long and fruitful life on the h6-f8 diagonal and ultimately played a supporting role in the final win for Black. I'd also note that White did close the position immediately with 7.e4 and Black offered to trade the Bishop for Knight on g5 and White declined and further Black quickly followed with f5.

Bottom line, I think that your assessment of the Bishop in this position is superior to that of the 1900+ player.

I think Be7 is not mandatory, you can just push g6 and fianchetto your dark bishop in Bg7, your position is a bit more flexible like this than with Bf6 and lost of tempo.

g6 Bg7 looks like a pretty reasonable idea, maybe with an eventual push of f5 and e4. I ran it through Fritz and it found a tricky little move though on the immediate 5...g6, white plays 6 Qa4+ Nbd7 (if Bd7 then Qb3) 7. Ne4 and everything is pinned up and Black has to move his king to e7 (or Be7 but then that defeats the purpose of g6)