Also how it takes to get assigned a CO in this branch?
There is no way to tell you, as it depends on how many applications are received and being processed at that office, which is not predictable.
The CO is going to be comparing the description of your job on ANZSCO with what your responsibilities are. S/He is going to check to see if you have to do something in your work that matches up with each part of the description, and there will need to be as many matches as possible. Look at the ANZSCO description, and think about your job in the light of it - what you can say, and what details you can give, to show the CO that yes, you do
that.
The CO will be asking your employer the same kind of thing, so be sure that your version and his/hers will match up. The CO will also ask the employer questions about the health of their firm - the financials etc. - to make sure your job is likely to be secure, as INZ don't want to issue visas to people who will shortly be put out of work if the employer goes out of business.