Why do you give 8...Na5 an exclam if you don't know
whether it is good? If anything it should be "!?" or "?!".
Some study material:

[Event "Kosenkov mem corr"] [Site "Russia"] [Date "1999.??.??"] [Round "0"] [White "Morgado,Juan Sebastian"] [Black "Malinin,Vasily Borisovich"] [Result "1-0"] [Eco "C88"] 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 0-0 8.a4 Na5 9.Nxe5
{9.Ba2 d6 10.d3 b4 11.Nbd2 c5 12.Nc4 Nxc4 13.Bxc4 a5
Grishin - Malinin;
9.Ba2 d6 10.d4 exd4 11.Nxd4 c5 12.Nf5 Bxf5 13.exf5 b4
Janos - Malinin}
9...Nxb3 10.cxb3 Bb7 11.d3 d5 12.Nc3 dxe4 13.Bf4 exd3 14.Nxd3 b4 15.Na2 Nd5 16.Be5 c5 17.Qg4 f6 18.Bg3 Kh8 19.Rad1 Qb6 20.Nf4 f5 21.Nxd5 Bxd5 22.Qe2 Bxb3 23.Qxe7 Bxa2 24.Rd6 Qa5 25.Rd7 Rf7 26.Qe8+ Rf8 27.Qh5 f4 28.Ree7 fxg3 29.hxg3 Rf7 30.Rxf7 Bxf7 31.Qxf7 Rg8 32.b3 Qb6 33.Qd5 a5 34.Rd6 Qc7 35.Rc6 Qd8 36.Qxd8 Rxd8 37.Kf1 g6 38.Ke2 Re8+ 39.Kd3 Rd8+ 40.Kc2 Re8 41.Rxc5 Re2+ 42.Kb1 Rxf2 43.Rxa5 Rxg2 44.Rb5 Rg1+ 45.Kc2 Rg2+ 46.Kd3 h5 47.a5 Kg7 48.Rxb4 Rxg3+ 49.Ke2 Rg2+ 50.Kf3 Rc2 51.a6 Rc8 52.a7 Ra8 53.Rb7+ Kf6 54.b4 1-0