I've written a couple of scripts in English, which is unfortunately not my mother tongue, and I need some help with a few words/lines. I don't have anyone else I can ask... 
Any help is much appreciated!
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- I'm looking for the name of the place where wastewater is filtered (sorry for the mental image!
) The dictionary is giving me many options so how would you call it?
- On a junkyard (or I guess I should say scrapyard when leaning towards British English?), what is the device called that compacts the old cars? You know, the one that people get murdered in.
- Where do people commonly go shopping and, among other things, buy cleaning products? Is that a supermarket? Or just store? Or..? And what would the salesperson be called? Salesperson?
Assistant? Clerk? Argh. I mean the person you walk up to and ask where the tampons are (or maybe not).
- This is supposed to be the first line, explaining the situation, but I'm very unsure whether it's correct:
Therapist: "What is it that made you seek couple's counseling?"
Any help is much appreciated!