Ann is in. An is usually "the" but in the question it's "a hospital" so not sure why they've used "an".
Anns an is in the, ann an is just in.
is mise ann an ospadal an-drasta
Not quite. It's tha you would use rather than is.
You use tha when describing something and is when identifying something. You are describing yourself as being in hospital rather than identifying yourself as being in hospital.
It would mean My name is In The Hospital Just Now.
Why do you have to put 'in' twice in a row?
"ann an" or "ann am" mean "in"-- "ann" by itself would not work.
Why an drasta and not a nis?
I believe the difference is an-dràsta refers to "now" meaning "at this very moment" as the above sentence states vs a-nis which refers to now in the sense of an opposite of a previous situation. I was sick but now I am healthy.