We're trying hard to make this both consistent and correct, but it isn't easy, I know it's far from perfect at the moment. flera does not really mean 'many', it means "at least 2 and preferably a few more", which probably makes several and multiple the best translations.
'many' is många.
Stage clothes for dressing up in e.g. the theatre are called kostymer. The same goes for children playing at dressing up. Hazmat suits, not so much - unless you're using them for a role in a play or a movie. :)
Another word for that is dräkt, and in fact both halloweendräkt and halloweenkostym are in use.
Thanks. Seems like these words work kind of similarly in Swedish and Finnish. In Finnish, we have the words puku (suit) and asu (costume), but we can similarly say either Halloween-asu or Halloween-puku (although the latter might sound a bit more clumsy).
An interesting quirk of Finnish: in the theater we have puvustaja (costumier, a person in charge of costumes) and puvustus (the art of making costumes / the whole group of people in charge of costumes), based on the word puku (suit). But the actual word for a theater costume is usually rooliasu (role-costume), which instead obviously derives from asu. Just found this interesting, thought I'd share!
Are you trying to ask about the English word has (a form of have) or the Swedish word has (a form of har) ?
The difference between English have and English has is first or second-person vs third-person: I have, You have, He has, She has, but in those examples both have and has can translate to Swedish har.