Black has a lot of viable options on move 3, you can choose QGD, Triangle Slav, different versions of Tarrash or even 3...a6. However, all of them require studying a serious amount of theory. How about cutting if a lot of theory with 3...dxc4? It looks surprisingly good for Black and it's relatively a fresh idea on the high level. As always, my file goes beyond the existing theory for both colors, especially that this line is quite fresh. No doubts in my mind, it will serve you for many years ahead!