Are the beginning of modules supposed to be difficult?

Outlaws of Alkenstar spoilers

Tonight I ran session 1 for my OoA campaign. All the players are new, with me being still fairly new as well. They got to the bank and cleared out the first area and ended the session outside the bank managers door.

My worry comes from the difficulty of the fight. For context, there are 2 patrolling clockwork guards outside of the bank, and when the party gets violent in the bank there are 4 mooks who attack them. It doesn't sound like much to me, since the clockwork enemies were level 1 and the mooks were level -1, but they kinda got mopped during the fight. They went past the clockwork outside, so when they got violent inside a mook went and alerted the clockwork guards. I don't think I was playing the enemies too smart or anything, the mooks just moved and attacked, or if they didn't have to move they'd attack twice and try to demoralize, and the clockwork guards just ran at them and tried to apprehend them or ignore them if they dropped down.

During the fight they didn't reposition a lot to try and flank enemies, but I think that might be because one of the players got AoO from the clockwork guards when they tried to move from them so that might have discouraged that idea. Other than that and not taking out the guards before going in the bank, they played perfectly fine but still got beat up bad. Is that first encounter actually hard, or is there something I can do to help them do more than scrape by?