What can I do against Fried liver attack?

if you want to keep playing the two knights after 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 play 4. ...d5, after 5 exd5 don't take the pawn back with the knight but instead play Na5, this is the mainline way to counter the knight attack

if you want to avoid the fried liver entirely try playing 3. ...Bc5 instead of Nf6, this prevents Ng5 because you can just take the knight

if you want something crazy and aggressive try the traxler counter gambit, its dubious but at lower levels white will probably have a hard time defending

You have two options. Option 1: you can play it safe by first playing d5; if Bxd5 you just Nxd5, and if they take w pawn you maneuver your knight to attack and chase bishop anyway... Option 2, my favorite: counterattack. There's Traxler counterattack (4. ...Bc5 5. Nxf7 Bf2+ 6. Kxf2 Nxe4+ and then assault king w other pieces), and a bit more solid Ponziani-Steinitz gambit (4. ...Nxe4, then either 5. Nxe4 d5 (pawn fork) or 5. Nxf7 Qh4 (again counterattacking the king))

Learn any anti fried liver traps