Questions & Answers about Komşum kapıyı çalıyor.
-m is the 1st person singular possessive suffix, meaning my.
- komşu = neighbor
- komşum = my neighbor
So the sentence literally starts with My neighbor...
Because kapı is the direct object (the thing being knocked), and Turkish marks definite direct objects with the accusative case: -(y)I.
- kapı = door
- kapıyı = the door (as a specific/definite object)
The -y- is a buffer consonant inserted because kapı ends in a vowel, so you don’t get two vowels in a row: kapı + ı → kapıyı.
çalmak has more than one common meaning. Two major ones are:
1) to steal
2) to play (an instrument) / to strike / to knock
In the fixed expression kapıyı çalmak, it means to knock on the door (literally “to strike the door”). So çalıyor here is (is) knocking.