Questions & Answers about Bu bölgenin modern olduğunu düşünüyoruz.
Why do we need the word olduğunu here? Can't we just attach a suffix directly to modern?
Why is the subject of the clause bölgenin in the genitive case instead of just bölge?
In Turkish factive clauses made with -dık, the clause acts structurally like a noun phrase. The subject of that clause (the region) becomes the 'owner' and takes the genitive case suffix -nin, while the verb takes the possessive suffix -u. It functions literally as 'this region's being'.
What exactly are the suffixes at the end of olduğunu?
It breaks down into olduk (the factive participle) plus -u (3rd person singular possessive, matching the region) plus -n- (a buffer letter used after 3rd person possessive suffixes) plus -u (the accusative case marker). Notice that the k in olduk softens to ğ because it is followed by a vowel suffix.
Why does the clause need that final accusative case marker?