In English, the defined use for "there" I know are:
The dog is there. (Location).
Once there was a dog who had no shoes. (Existence).
There was a man who lived there. (Existence in first part of sentence.); (Location in last half of sentence.)
There was a man who lived here. (Existence) (Location).
The pronunciation is correct. The sound for ㅁ is only approximated by the sound for the English "m".
Good reference: https://www.youtube.com/watch?v=zhf9NWKHjqE
Essentially, the Korean sound for ㅁ is similar to the English "m" without the windup, which can sound like the English "b".