When asking questions?
 

When you ask a question you add ka but what about when you use da at the end of a sentence.

Like I hear nan desu ka and nan da but not nan da ka.

Da ka just sounds weird to me as well.

da is less formal, and masculine. "Desu ka" becomes "ka" when it less formal. So "da ka" wouldn't be used.

Oh. Thanks!

That clears up soooo much.

Da is masculine?

何だか[なんだか][nandaka]=somehow, when you're unsure of something

e.g.
なんだか吐き気がします
Nandaka hakike ga shimasu
I feel like thowing up

何がなんだか分らない
Nani ga nandaka wakaranai
I didn't know what was that

何だかすごく疲れたね
Nandaka sugoku tsukareta ne
Somehow I felt really tired

"Nandaka" is a very common expression and is taught when in either level 3 or level 2 standard.

That what i want to say but I just couldnt express it.
Enyafriend must be very good at Japanese.
I dont know how to explain Grammar in English,
for English is my ESL.

If you're talking about how to ask a question in casual form (that's when you end sentences in da instead of desu) it's like this:

Formal: Nan desu ka?
Casual: Nani? (with questioning intonation)

So aside from "nandaka" meaning "somehow" or when you're confused about something you don't get "da ka" together. I believe your question was aimed at the casual style questions, so just say the sentence like usual, but end with a questioning intonation.

Make sense?