My parents visit grandpa every weekend 

=> (-) My parents don't visit grandpa every week.

=> (?) Do my parents visit grandpa every week ?

i surf the internet in the morning

=> (-) I don't surf the Internet in the morning

=> (?) Do I surf the Internet in the morning ?

Chúc bạn học tốt

(-) : phủ định

(?): nghi vấn 

1) My parents visit grandpa every weekend. (chia hiện tại đơn)

⇒ Phủ định: My parents don't visit grandpa every weekend.

⇒ Nghi vấn: Do your parents visit grandpa every weekend ?

2) I surf the Internet in the morning. (chia hiện tại đơn)

⇒ Phủ định: I don't surf the Internet in the morning.

⇒ Nghi vấn: Do you surf the Internet in the morning ?