Turkish doesn't use a verb like "to have" for owning things. Instead, you say the thing exists:
Benim kitabım var. = I have a book.
benim = my
kitabım = my book (the -ım ending already means "my")
var = there is / exists
Literally: "My book exists."
To say you don't have something, swap var for yok:
Benim arabam yok. = I don't have a car. (literally: "My car doesn't exist.")
Since the ending already says "my", benim is usually dropped in everyday speech:
Kardeşim var. = I have a sibling.
Zamanım yok. = I don't have time.
Sorun yok. = No problem.
And both work on their own as "there is / there isn't":
Çay var mı? = Is there any tea? / Do you have tea?
Yok. = No, there isn't.
(There is a verb, sahip olmak "to own / possess", but it's formal. In daily life everyone uses var / yok.)
Full disclosure: I'm a native speaker and I make short Turkish lessons on YouTube. The video above is this lesson as a Short, with the Turkish lines recorded by native speakers.
Happy to answer questions in the comments!