Complex sentence: Because of Wally, Barry is now aware that the timeline is not reset correctly after Flashpoint and thus another alternate timeline, though he cannot completely remember his pre-Flashpoint life, such as the original Flash Jay Garrick.
Split into simpler sentences: Because of Wally, Barry is now aware that the timeline is not reset correctly after Flashpoint and thus another alternate timeline. He cannot completely remember the details of his pre-Flashpoint life, such as people like the original Flash Jay Garrick.