Study the rules about how to use personal pronouns:
https://learnenglishteens.britishcouncil.org/grammar/beginner-grammar/personal-pronouns-possessives
And do the activity on the following worksheet:
Study the rules about how to use personal pronouns:
https://learnenglishteens.britishcouncil.org/grammar/beginner-grammar/personal-pronouns-possessives
And do the activity on the following worksheet: