When you make possessive construction in English, it is generally very simple as you line two nouns in a sequence as in Turkish tea. However, in Turkish, there are several rules to that. I don't think you guys cover that grammar rule in A1 Turkish, so I won't bother you with this.
Just know this: "Türk çay(ı)" => the letter (ı) in the end of the word tea makes the tea belong to the Turks.
Let me give you some other examples: --> Flag pole: Bayrak direğ(i) --> Door knob: Kapı kol(u) --> Human voice: İnsan ses(i)
All the suffixes above added to the second words indicate that they are attached to the meaning of the first word. Pole is not just a pole, it is a pole for a flag whereas it should have been a pole for construction. Knob is not just a knob, it is a knob for a door whereas it should have been a knob for a case. I think you got the idea. Have a nice day.