Learn the Réti opening
The Réti opening begins after 1. Nf3.
This opening is sometimes referred to as the "Zukertort" Opening. Your opponent has many responses, many of them being 'invitations' to different openings. For example Nc6, will likely transpose into a king's pawn game. We play e5 and after they play e5 I would recommend the Scotch game, which lucky someone made a blog about
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They have the Sicilian Invitation witch c5, if you know the Sicilian, play e4, if you don't, play c4 and learn the English(assume I have a blog on these openings). If they play c6, this is the Slav invitation, learn the Queen's Gambit or the simpler Slav Defense. If they play d6, the Pirc Invitation, learn the King's Indian Set Up. If they play e6, the Queen's Gambit Invitation, learn the Queen's Gambit. If they play f5, learn the Dutch Defense.
If they play e5, this is the Ross gambit. Take their pawn, if they kick your knight with f6, play e3 to play Qh5+. If they play d6 or anything similar, move it back.