prep against d4 d5 e3

Just a developing move developing your queen and trying to go for a attack on the king

I feel like Nd3 in that position isn’t so good because after e6 by black, he threatens c4 with tempo which makes blacks queenside attack much faster.

Hardly an original game: this kind of strategy against the Stonewall Attack, which promises Black at least a slight positional advantage,  is known since ages.

The Stonewall Defence is a good, solid option for Black: it works positionally because of the relative inactivity of the fianchettoed g2 bishop. Quite ironically, the Stonewall Attack, with a tempo more, does not work because Black has not played ...g6 yet, and can comfortably deploy both his bishops at their favorable squares.

Recently I saw a course on Chessable, named "The Yaac" or something like that- it's a course for white advocating the Stonewall Attack.

Out of curiosity, i looked at what is suggested against the above line. The suggestion is shocking: "Black is better, but it is unlikely that you will meet this over the board".

Pure genius, don't you agree?

I suppose that's true, but both players lose a tempo doing so. Black for having to develop his knight himself and white for having to move the knight.

play Nf6 not d5

Mr.pfen's suggestion is also quite convincing.

Thanks everybody !!