If we have qadha namaz then can we offer namaz e shab or other sunnat namaz? Or frst we'll have to offer qadha prayer?
Can we get the sawaab of both simontaneously? Like if it's possible?

You can. However, it is much preferred that you make your qadha prayers, as they are wajib, while most of the mentioned prayers are not proved to be really narrated by Imams PBUT.