> 添削してくれてありがとう.
いえいえ、どういたしまして。

> I thought about using "wakarimasen" instead of "shirimasen," but wasn't sure which was better.

Maybe it depends on the context, but at least in the case like that, using "shirimasen" gives a colder impression to the listener, I think. Somehow "shiranai" has a bit cold or rough or refusing sense as compared with "wakaranai", it seems to me.

> Is "no ka dou ka" always better than "no ka" for expressing "whether"?

I think so. Just "na no ka" sounds lacking something.

Shizu

Konnichi wa tony san to shizu san.
Setsumei shite bunshou o naoshita (kureta?) arigatou, kedo hitotsu koto ga mada wakaranai kedo. (Kedo was used to "soft" the sentence,right?)
Ok,i didnt understand the usage of -na no ka-.
It means -whener? I even dont know that word in english, lol! Motto setsumei kurenai ka/kurete mite(donno how to ask correctly)

X da = X is the case, X is true
X na no ka dou ka = whether (or not) X is the case, whether (or not) X is true

kono anime wa taikutsu da.
This anime is boring.
kono anime wa taikutsu na no ka douka, wakarimasen.
I don't know (wakarimasen) whether (or not) this anime is boring.

I think I understand the usage Shizu-san gave of "na no ka" without the additional "dou ka," but I can't think of a convincing way to explain it in English (and I don't know your language).

> Setsumei shite bunshou o naoshita (kureta?) arigatou, kedo hitotsu koto ga mada wakaranaikedo.

Setsumei shite kurete, bunshou o naoshite kurete, arigatou. kedo hitotsu dake mada wakaranai n da kedo.

> (Kedo was used to "soft" the sentence,right?)
Mmm, I think that you can think so in this case. "kedo" is more conversational rather than written expressing, so accordingly it sounds softer because written expression tends to give formal and hard impression.

> Motto setsumei kurenai ka/kurete mite(donno how to ask correctly)

Motto setsumeishite kuremasen ka?

wakarimashita, yattemimasu.
Okay, I'll try.

There is a person in front of you. The person has long hair, but doesn't look so feminine. But you can't believe definitely if the person is a man. In such a case, you may say in your mind:

kono hito ga otoko na no ka dou ka wakaranai.
I don't know if this person is a man or not.
or
kono hito ga otoko na no ka onna na no ka wakaranai.
I don't know if this person is a man or woman.

I hope this helps,
Shizu

Konnichi wa.
I think i got it now, i think lol.
So, -na no ka- = whether... and -na no ka dou ka- whether is or not...

But can i use -na no ka- alone, without -dou ka-, like:
Maniau na no ka, shiranai- i dont know whether i will get in time(or not)
Or i didnt got the point =P

Could you explain meaning and use of -na no ni- while we are still talking about -na no... stuff, please?

> So, -na no ka- = whether... and -na no ka dou ka- whether is or not...
I think that you can think so.

> But can i use -na no ka- alone, without -dou ka-, like:
> Maniau na no ka, shiranai- i dont know whether i will get in time(or not)

This should be:
Maniau no ka dou ka, wakaranai.

Without "dou ka" sounds awkward, at least in the sentence like above.

> Could you explain meaning and use of -na no ni- while we are still talking about -na no... stuff, please?

"na no ni" works as "but/although/though" as follows:

kono uta wa sugoku yuumeina no ni, tomodachi wa shiranakatta.
This song is very famous, but my friend didn't know it.

[ na-adjective + no ni ]
or
[ noun + na no ni ]

When using "na no ni", the speaker's surprise or unexpected feelings are expressed. In the sentence of above, the speaker is surprised that his friend didn't know the song
although it's very famous.

Shizu