Thanks for your suggestions, they are appreciated.
Well, back to the roots.
If the Qxd5-Scandi scores bad against the correct White setup, why not have another look at the Nf6-Scandi? I mean, it would be great to have a new opening that from the first moment on makes White play my game and this is the Scandinavian. I at first moment did not want to study the 2...Nf6 because with 4. d4 instead of 4. cxd6 or 4. exd6 White can transpose to the Caro-Kann or French.
The second look showed me that the danger that White transposes, is in the Islandic Gambit very low. At the Scandinavian Gambit (3..c6) the likeliness of a tranpose is very high, at Chessbase 8.0 at about 80 % ! But at the Islandic Gambit (3...e6) only 22 % of people transpose to the French Exchange. And even if they do, you have a boring French Exchange that offers Black immediately a good position with a score of 52 % white to 48 % black.
So why not go for the Nf6-Scandinavian (and the Scandinavian Gambit)?
The by far most common third move there is the 3. d4. I went throught all different variations and think that after 3...Bg4 (I think this is called Portugese variation, isnt it?) Black get always a good tactical fighting-position that has good scores for black.
Also after 3. Bb5+ Bd7, 4. Bc4 Bg4 or 4. Be2 Nxd5 etc. black scores good.
The only way for White to cause black serious problems seems 3. c4 e6, 4. dxe6 Bxe6, 5. Nf3. Somebody in another thread said 5...Qe7 is best. Would never play this! After 6. Qe2 Nc6, 7. d4 black is either in serious problems or cant avoid (Bg4) that White can change the Queens and then have a game that scores 72 % for White! So I would go for the 5...Sc6
One basic question remains: does Black get for the pawn (if White keeps it) get enought play or can White stand the black attack and have the better end in the endgame?