In a few situations I would say you could safely translate hverdag to "everyday". Example: "Han har en vanskelig hverdag" would be understood as similar to "His everyday life is hard/difficult".
Hverdag is without space between the two words unless you want to say every (single) day. See comment by Griffindd where the usual translations are given.
Do Norwegians actually use "hverdag" as "a working day"? I have always used "en abreidsdag" (as a working day) and "hverdagen" (as everyday/daily life). I guess it's not a mistake, but I'm wondering what is more common?