This is a nice opening you can play as white

That is a miserable position to play with black.

yup, thats why the opening is so good for white :D

4....f5 5.d3 - 'with a good position for White' - looks ok, but Black's still a pawn up after all.

But white has lots of compensation for it, thats why its a gambit you give a pawn away to regain it later.

Of course, 5... Bb4 is a substandard move, Be7 or Nbd7 seeem better and 6.... Bxc3 is terrible, Qe7 makes much better sense if you're going to play Bb4.

Yup, Be7 was played by a Grandmaster, bxc3 is bad because opens up the file for the rook.  is it possible to post videos here? I will post a series on this gambit.