Learn Turkish: Sırf beni aramadın diye bana kızgınsın zannettim. - I assumed you were angry at me just because you didn't call me.

In Turkish, you can create an informal 'because' clause by taking a complete, conjugated sentence (beni aramadın - you didn't call me) and adding diye right after it. When combined with sırf at the beginning, sırf ... diye translates perfectly to 'just because ...'.

Why do we use beni in the first part but bana in the second part?

This comes down to which case the specific words demand. The verb aramak (to call) requires the accusative case, so 'call me' is beni aramak. On the other hand, the adjective kızgın (angry) requires the dative case for the person you are angry at, making it bana kızgınsın.

Is kızgınsın functioning as a verb here?

It is an adjective (kızgın) with the personal suffix (-sın) attached to mean 'you are angry'. Because the main verb of the whole sentence is zannettim (I assumed), the phrase bana kızgınsın acts as the direct thought you are assuming: 'I assumed that you are angry at me'.

Why does the verb zannettim have a double 'n'?