Is there any important difference between arbeider and jobber?
Not really, but 'jobber' is used more often colloquially.
So 'the engineer's working with me' is wrong??
Ive found that Duolingo doesnt like contractions very much, try to avoid them as much as possible
As in, the construction's right, but the contraction is ambiguous, so try to avoid it.
Why not "is working "...???
does the -ng make a -sh sound like sj and skj and -rs? sounds like "in-shen-i-ur-en."