Judging from sources b and c what was it like for the average soldier in the trenches

Before the battle began, usually soldiers are made to do several repetitive things, such as Stand downs-get ready for the attack; Breakfast and Weapon cleaning, Inspection, and Chores.
After the battle, the trenches became a nightmare. Since a lot of dead soldiers lying on the trenches, the smell was really unbearable and the whole place always invested with rats