How to beat the Keres Attack in the Scheveningen Sicilian

You're asking a question that has no easy answer. The Keres Attack is formidable and success against it is not a simple matter. The first choice Black has to make is whether to play 6...h6. That move restrains White's g pawn temporarily but weakens Black's K side and gives White a hook to tear it open.

In most variations, Black develops the QN to c6, leaving d7 open for the KN if White manages to force g4-g5.

This variation is very complex, and it is difficult enough that (I've read) Kasparov stopped playing the Scheveningen directly and started entering it through the Najdorf move order. That, of course, has its own problems, specifically 6. Bg5 which is stronger against the Najdorf than against the Scheveningen.

Sorry not to be of more help. For more detailed information, you might check Lorin D'Costa's  "The Sicilian Scheveningen Move by Move". It has almost 50 pages on the Keres Attack.