Iam an German aupair , finishing my second year in December , a company offered me a full time job with sponsoring , am I able to change my visa or are they able to change it for me ? If yes ,what visa should we aim for ?

WHat country would this be? Ukraine, Romania, South Africa, Canada?

I'm in the US

Not enough info, but keep in mind that only certain jobs would allow non-resident to apply for work visa. Nanny/caregiver is not one on the list.