i got this line in a bulletgame that i lost early on time but i got interested in the idea. i put some annotations on the moves. can it be healthy of me to grab so much space? white did look underdeveloped so i like the idea
ehm and im black. im interested in this from the black side
No, White shouldn't expect to make anything out of it. Black just plays ...cxd4 5 Nxd4 Nf6 with idea of ...e5 (if White belated tries 6 cxd5 Nxd5, still with the idea of ...e5). Black looks fine.
While the isolation of the QP isn't bad for Black of itself, it remains White's best chance to find an edge in an unbalanced position. Sitting back and allowing Black to initiate the central exchanges as it suits him just isn't "proactive" enough.
Usually you should expect 4...Nc6 from a "pure" Tarrasch player, although I see nothing wrong for Black after 4...cd4 5.Nxd4 Nf6. After 4...Nc6 though white may try 5.dc5!? trying to get a good version of the dc5 variation, although I believe Black is OK after 5...d4 6.Ne4 Nf6.