Here and in the next moves, it would be better to play a7-a6 and avoid White's counterplay on the queenside.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. d1c2  4... e8g8  5. a2a3  5... b4c3  6. c2c3  6... d7d5  7. c1g5  7... h7h6 7...dxc3 and 7...c5 are popular alternatives. 8. g5f6  8... d8f6  9. g1f3  9... d5c4  10. c3c4  10... b8c6  11. c4c3 This move is necessary to fight the e6-e5 advance. All this is still theory. 11... f8e8  12. a1d1  12... e6e5  13. d4d5  13... c6b8  14. e2e3  14... c8f5 The computer's favorite move. Caruana, as always, shows impeccable preparation. 15. f1e2  15... b8d7  16. e1g1  16... a8c8  17. a3a4 A new and somewhat strange move. Niemann  spent some time here, so I believe this was not preparation. 17... c7c6  18. d5d6 A brave move. The d6-pawn is passed, but it can also become a weakness. 18... c8d8  19. a4a5 White's idea pops up. The pawn heads for a6, breaking Black's structure. 19... f5g4  20. h2h3 This move leads to problems. 20... g4f3  21. g2f3 A sad necessity. The endgame is much better for Black after 21.Bxf3. 21... d7f8  22. c3b4  22... d8d7 Now Caruana has a much better position. 23. d1d2 