Ah a Fellow South African! Welcome to YT
I would first think about what health and genetic tests were done on the originally bred female and the stud used?
If you are really serious about breeding, I would search out as much information as possible, test your female, and find a breeder near you to mentor you.
This is a serous decision, and I can tell that you you care about your yorkie, so I'm sure you are doing all you can to inform yourself.
Have a look around here in the breeding section and the YT Library. That may be a good start
Good luck doll