Remove drywall before putting up a wall?

If you are putting up a stud wall you can fix the timbers to the dry walling by locating the existing studs and nailing right through the d/walling, but it would be better if you screwed it, this way you avoid causing too many cracks. To build a stud wall you lay down a 4x2 sole-plate (screw it to the floor) you then install the uprights (studs) at 16in centres (can be 18in). These are skew nailed or screwed into the sole-plate and across the top of the studs use the same dimension timber as the sole-plate. A third and two thirds of the way up you need to put in noggins between all of the 4x2 studs to stiffen the wall up. When you leave an opening for a doorway (interior doors are normally 30in wide) the opening should be a shade over 31.5in. (the door casing is 3/4in thick on each side) The width of the casing is dependent on whether you are using plaster-board or other material. I assume by anchor bolts you are referring to the screws I said to use to fix the sole-plate. I hope this lot is clear enough to understand. Anything else that might puzzle just post it and I'll get back to you.

you have no clue to what your doing,

all you have to do is find the studs cut the drywall out for the door

frame it in