Hi! Hope this helps, but if you are stuck interacting in the store:
Spoilers on how to progress:
Grab the cleaning supplies from the backroom.
Make sure you clean the mess in all the aisles + the bathroom.
You will then need to go outside the store door and into the alleyway (there is a bunch of graffiti on the wall).
I missed the last part myself, but at this screen, if you hover near the bottom it will say 'check staff door'. Click on that and check the staff door and then go back to the store.
If you see an old man talking about his dogs when you enter back in, you should be able to progress with the rest of shift 2!
Hope this helps! <3