Should I pray my Qada salah or pray extra nafl salah?

Salam. I don't know what to do as I hav heard two opinions on this question. I heard that praying Qada is useless, and that one should just make extra nafl salah to cancer out those missed fard prayer, but I also heard that one should not pray any nafl until he/she has made up their Qada salah? So what should I do? Oh, and can everyone please pray for me. I am really ill, and I think that my time is very limited (God forbid) But please just pray for me and that Allah excepts my repentance. I never use to pray of fast, but Alhamdulilah I have been guided and am making an effort :) JazakAllah Khairan, Wasalamu'alykum w.b. May Allah guide us all Insha-Allah to the straight path and grant us all Jannah. Ameen :)