After 1.e4 e5 2.d4 f6 White has a winning tactic. Try to figure it out.
What to do when my Danish Gambit gets declined?

If you don't know what to play after 2.d4 f6 then I suggest studying elementary tactics, and forgetting about openings.
Study tactics but keep playing the Danish Gambit because that will improve your tacics as well.
This post reminds me of Jackfast's post. He said he had to stop playing the Danish because of the refutations. When I asked what specific line was giving him problems he posted a position where Black had played f6. (also Black seemed to have gained four tempi somewhere in the position he showed).
I've only had someone use the line Pfren showed in his article against me once, and I'm pretty sure that guy was using an engine because all his move times were the same.
If you mean to kill the pawn on e5, I have had this happen and I end up losing (not sure if it's because the double pawns on the E file is 'weak' - ?? i have no idea, I'm pretty new and I was just checking to see if there was something obvious I could study as a backup in case the gambit is declined.
Also, when studying these established openings, if someone doesn't play exactly the lines you tried to learn, should you stop playing the lines? I also learned some basic moves in the Sicilian, but it's pretty rare that, after 1. e4, c5; 2.kf3, d6 suddenly white decides to play d5, like they are 'supposed to' in the Sicilian. In these cases, is it bad if you keep playing your opening? Or does the opening also lead to a good overall 'shape' of your pieces so that you will still have a strong position even if the other side doesn't follow the lines exactly? Make sense what I'm asking? Thanks in advance to any answers!
I found some videos on the Danish Gambit and started playing this in my OTB games and I think it's so cool! I'm new to chess but have been beating my (also relatively new) friends consistently as long as they fall for the gambit. (Although once I use it on someone, they usually never accept it again)...
My question is: I have no idea how to respond after 1. e4, e5, 2. d4, f6 (or, 2.d4, c6)... in otherwords, how do I respond when black decides not to take my e4 pawn but instead, to backup his e5 piece with a pawn or a knight - are there still 'good' opening lines I can study to play in response to any of these? If so, what are some names? I would like to have a backup 'opening' to revert to in case black doesn't go for my d4 pawn. THANK YOU!