Ich habe ein Buch.
English: I have a book.
The verb 'haben' shows possession and relationships. At this level, treat it as a high-frequency helper word, similar to 'have' in English.
Use 'haben' for things people own, features they have, or simple personal information.
Ich habe ein Buch.
English: I have a book.
Er hat eine Schwester.
English: He has a sister.
Sie haben keine Zeit.
English: They do not have time.
Sie hat ein neues Handy.
English: She has a new phone.