Is this correct?

Only you asked if we are coming to Turkey.

Sadece sen Türkiye´ye gelmediğimizi sordun.

Türkiye´ye gelip gelmeyeceğimizi sadece sen sordun. 

* here we use future tense because the action ´´we are coming to Turkey´´ not happened yet. 

Thankyou!.

So why is there ´gelip´ that looks like there is come twice. And how do we know the ´me´ is not negative?

What does the sentence I wrote mean - or someone would interpret it likely the same but it´s wrong grammatically? 

The gerund -IP itself does not convey a specific time but it builds a connection between two verbs.   

Verb stem positive +ıp ip up üp +  Verb stem (same verb) negative  +  ecek/acak  + possessive ending + case endings if required

The above formula is used when translating the sentences where WHETHER and IF could be used interchangeable  in English. 

verb gelMEK come twice in your sentence  yes.  It is how we construct this type of sentences.

We know ‘’me ‘’ is negative because of positive is not possible with this structure. 

In Turkish mind we form that type of sentence as --------

Only you asked whether were coming to come to Turkey OR (we are ) not (coming ) .

 Türkiye´ye gelip gelmeyeceğimizi sadece sen sordun. 

The problem with your original sentence is , there is mistake in terms of grammar, therefore the meaning is not clear.. unless we add ‘’ gelip ‘’  before ‘’ gelmediğimizi ‘’

Sadece sen Türkiye’ye gelip gelmediğimizi sordun.

In that case ‘’the meaning ‘’ will change-----------Only you asked if we came to Türkiye (or we didn’t come to Türkiye)

The sentence becomes past tense sentence.

Thanks I think I get it now.

Sort of like: ... whether we are coming or not coming

Yes, kind of ..  

You can say that sentence in a diffent/more simple way , using

.......diye sordun.   (you asked saying...........

´´ Sadece sen ´´ Türkiye´ye geliyor musunuz ? ´´  diye sordun.