1.e4 e6 2. b3!?

a week ago i played against a player with black like this:

any1 knows how black should play now and whats the name of this line?

Well, the name is Spielmann Variation, also known as Réti Variation.

When you can find information on Spielmann-Müller, Vienna 1928 and Spielmann-Grau, San Remo 1930, as well as Réti-Maróczy, Göteborg 1920, you can see what the name-givers did.  

ok tyvm guys :D

i suggest pushing with d4 just continuing with the main line 

Oh, please, I don't want to be annoying or a pedant who always knows better, but sorry, Pellik, 2.b3 itself is not a Gambit;  --   and the Réty Gambit is as follows  Nf3  d5  c4  dxc4 ,  ( dxc4 is gambit Accepted ).  And yes, the books give more info !  Best regards !