Responding to the Ruy Lopez

I got to a postition in one of my games and was wondering if any of you guys had an idea about what black should do.

I think Black should take the bishop with the d pawn, and if the Knight takes the pawn on e5, the queen comes to d4. I'm not sure though...

Is this game ongoing?

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 dxc6! looks much better for black.

If 5.Nxe5 then 5...Qd4 or 5...Qg5 are adequate to regaining the pawn.

Thank you for confirming that 

No, the game has already finished.

After Nxe5 then Qg4 will be enough to regain the pawn

In that position, 6... d6 regains the pawn after 7. Nc4 Qxe4+ 8. Ne3.

But the 4... dxc6 is the main line.

In move 4 it's tempting to finish the exchange by capturing the Bishop using your b-pawn, because of the general principle that if there's a choice of which pawn to use, it's better to capture by the pawn that moves toward the center file.

However, in quite a few openings involving capturing a White piece on c6 , dxc6 is listed as preferred.  It opens up nice lines for both the light-square Bishop and the Queen, and avoids leaving an isolated pawn on the a-file.

If you do capture with bxc6 , the one benefit you get is the semi-open b-file, which you might want to take advantage of by sliding your Rook over to b8.  In this case it won't have an immediate effect, but Rooks thrive on open and semi-open files.  With respect to semi-open files, I was taught to think of a Rook like it's a cannon.  Just because there's a wall in front of the cannon doesn't mean the guy standing on the other side of the wall shouldn't be worried. 

--Cystem

What if white plays 7. Nxc6?

Yeah 4. ..dxc6 is probably better than taking with the b-pawn. If white gives up his bishop for the knight, you want to open up the center so your bishop pair will have more scope.

While 5. Nxe5 is bad when black has played 4. ..dxc6, I'm not so sure about it here.