Wow, this is hard to explain....
Let's say for instance: kangaroo (this is how you suppose to pronounce it: KANG-GU-ROO). from the word 'KANG', omit the 'K' and you will have 'ANG' - pronounced as spelled. Try to omit the 'A' and you will end up with 'NG' that when promounced, it uses your throught and breath comes from the the nose and not the mouth. This sounds a bit odd as if you're just humming a sound of it. Finally, you add an 'A' to the last part of 'NG', making it 'NGA'. The 'A' would be a hard and very short when pronounced just like"at" or "cut".
"NGA" by definition would mean: "surely" or certainly", or could be a word to express politeness.
ex: "Oo nga!" - 'yes, for sure' or 'yes certainly'
"Pahingi nga?" - "Could I have some?"
"NG" can be pronounced as "nuhng (nang)", but i don't think english has this word. Let's just say "evening". "NING" is pronounced as is, right? replace "i" to "a" and you'll get to know how to pronounce it.
good luck!
:)