Private/Corporal Horis Wright

My Great grandfather, who fought in the great war in the Royal West Kents as a sniper. My grandfather beleives this is the right Battalion, although his father never spoke of the war again. Horis wright was 17 when he joined and arrived in the trenches, either in 1916 ( the somme?) or 1917 ( Cambrai?). he was promoted to lance corporal then up again to Corporal, then for some reason was demoted back to the ranks. i would like any help in finding more information about my Great grandfather life in the war, where he fought and what he went through for me and my Generation. All informal sources would be greatly received
thank you for any information, Phil (16)