In this diary's it's not clear for me (or I don't understand), if they bomb the enemy or they are bombed themselves.. a lot of times he just mentioned "shelled.... etc. " Sorry, probably due to my insufficient English in this matter.
It's not 100% clear I agree (nothing wrong with your English!), but I think where they say "shelling more or less normal" and "machine gun fire active during early part of evening" they are talking about the enemy firing at them, or at some part of their line. Then when it is their side doing the firing they say "our artillery put up a barrage".