How can I deal with bxf2?

Don't panic, make the most active moves possible, develop your pieces quickly whilst preventing checkmate threats. Remember in this situation your opponent has made an unjustified sacrifice and you therefore have a better position. All you must do is ensure your king is safe (eg castle by hand Nf3, Re1 or Rf1, Kg1). So look carefully to find the best moves because if you do you will be winning.