they change when gender and tense changed.
turkish is devoid of grammatical gender,the third person pronoun "o" does duty for he,she,it .gelmek means to come. o geliyor. He/she/it is coming.(present tense).
The person of verbs are shown by suffixes but a pronoun in the nominative may be used for emphasis. gitmek means to go. o gitti, ben gitmedim.he went, i did not go.(past tense)
Turkish is quite complicated by nouns,adjectives,verbs..ect
good luck with it.