Do not try to memorize the whole 50,000 lines. Use the feature in ChessBase or the Training Mode in SCID. Set the software to hide the next move; you play the Plichta recommendation.
If you are a club player (1200–2000 Elo) who wants to stop losing to the Petroff or drawish Berlins, is arguably the most efficient study tool ever created for the classical 1.e4 player. Chess Lifetime Repertoires Plichta-s 1 E4 E5 7z
Upon extraction, the user typically finds: Do not try to memorize the whole 50,000 lines
Against , Plichta recommends a positional, Italian-style approach rather than sharp mainlines like the Ruy Lopez (though he includes robust alternatives). The exact PGN should be consulted, but typical Plichta recommendations include: the user typically finds: Against