How did the new kind of fighting seen in world war 1 affect the soldiers

Great question, so in WW1 a certain style of fighting was used, it was known as trench warfare. Trenches were built 300 miles long across Europe, and both sides, the Triple Entente (Allies) and Triple Alliance (Central Powers) would dig deep trenches to fight in.
Now one important part of WW1 was the creation of new weapons to give an advantage to the soldiers. One important on the Central side (German side) was the creation of the mustard poison gas which when thrown to the enemies would require the use of a gas mask otherwise you would die. Fun fact Hitler and his group of soldiers during WW1 were once hit by a poison gas and when he tried putting his gas mask on, his long mustache prevented the gas mask from sealing properly, but luckily for him he survived and afterwards he cut his mustache into a small stubble on the top of his lip that is now known as the iconic Hitler mustache. Anyway poison gas was a very good weapon against the allied powers and really harmed the soldier not only physically but mentally as it scared soldiers. Trench warfare as a whole was very depressing and scary for soldiers so to answer your question directly trench warfare was the new kind of fighting scene during World War I and it affected soldiers by causing them to become very depressed very scared and traumatized.