what to do after d4 f5 d5

because after bc4 my knight can't go in c3 for the rest of the gameeven if I play c3

Your comment doesn't make sense. Try again.

After 1.d4 f5 2.d5 Black should be happy that White gave a tempo.

But what does your "bc4" mean? and what has it to do with c3?

In the scandinavian opening I play bc4 in this position but do you have an other possibility.

I play c3 to do nc3

I really don't understand. The Scandinavian is 1.e4 d5. How do bc4 appear?

And do you mean Bc4 or bxc4?

How and when do you play c3?

sorry it's this:

e4 d5

e5 f6

exf6 nxf6

1.e4 d5 is fine

2.e5 is a mistake. White wins space, but lose momentum. Better play 2.exd5 to get developed pieces with tempo.

2...f6 is a big mistake. Don't fool around with the f-pawn without good reason. White would like to play d4, Black should play 2...c5 to meet this idea. I understand that you are afraid of the future of you Knight, but it can probably develop fine at e7 or even h6.

3.exf6 is also a big mistake: White helps Black to develop and exchange a strong e-pawn for a weaker f-pawn.

Thank you (you are the best)