Error Detection

What are the principal languages spoken in the following countries: the USA, the Netherlands, the Denmark?

When I was a child, I can went to the roof of my house and saw all the other houses and streets.

Who was a boy you were talking to just now?

"The Old Man and the Sea" is a novel writting by Ernest Hemingway.

I'm studing English at an English conversation school too times a week.

When I entered the classsroom, the teacher didn't say nothing, he went on explaining the meanings of the new words.

I'd like knowing where you are.

Olha is a good pupil and a best chess player in our class.

She is so a nice girl. Everybody likes her.

May you, please, help me with this task?

This is a shop where we bought the tape-recorder two days ago.

I didn't go to dinner with them, because I had already been eaten.