Bismihi ta'ala
Your priority is fulfilling your wajib, and then turning to nawafil. If you were to pray your qadha` prayers during the time of your nawafil, you will also be granted reward as well. So, as long as you have qadha` prayers, you should not be doing nawafil, and with a good routine for qadha' prayers you will be able to finish it in an adequate time.
And Allah knows best.