You didn'T lose in the opening, so there's no reason why you should "keep praticing" the vienna opening (of course to improve, but no other reason), you let go of too many pawns and he got you in the endgame that's all.
After !5... Qxd1 white should recapture with 16. Rfxd1 so if the Kt goes to c4, then the Rook on the a file protect the a pawn. and you can play b3 to push out the Kt. You have a winnning game. you have bishop vs KT. Black have too many pawn islands. I suggest study more on the end game and postitional play. You will have no problem winning these type of ending. Good luck!
apparently i should have kept practicing.
i have included sporadic comments on where i think i went wrong, but i would love to hear your input / opinions!