"I do not want to open this."
Translation:Nie chcę tego otworzyć.
Nobody says "nie chcę tego otworzyć" - We say "otwierać"! It of course means the exact same thing, but in this context sounds much much better.
Yes, we do! Both versions are equally correct (ie when you are looking into the sealed box and you don't want to break the seal you can say "Dlaczego jesteś taki ostrożny? Nie chcę tego otworzyć" ('Wy are you so careful? I don't want to open it')
But I have to agree that "otwierać" in a general context is looking a lot better.