Hi could you please tell me if this is right grammar

It's not right. The last part should probably say "... but one thing is for sure, I know it was worth it".

My best guess at correcting the first part is "I don't know whether the prevailing something [feeling? impression?] was (one of) coldness or beauty". However, the sentence as a whole doesn't really make enough sense for me to be sure what you mean. Can you give s

Basically I saw my friend's photograph of a place where she has been recently and she uploaded it on facebook, there is a comment under the photograph that says:

I don't know what the prevailing was coldness or beauty but one is for sure it was worth it, one of the most beautiful and amazing things I have seen

That is the complete sentence so I was wondering whether it's correct

The sentence is confused and ungrammatical. Assuming it was written by someone who had visited the place, my previous suggestion seems to make sense, and may have been more or less what was intended. It is not very clear what was "worth it". Making the journey there perhaps?

This is the best sense I can make from it. It seems like a place on a high mountain where the air is very cold.

I don't know what the prevailing if it was the coldness or the beauty (of this place), but one thing is for sure; it (getting there) was worth it. It (this place) was one of the most beautiful and a