A few grammar errors

Hey guys (/Author)

I noticed a few grammar errors in the story and thought it would be good to let you know.

In class 'Friends' "Connections can be repeated in the initial data, but inside it store once." "but inside it is stored once."

In remove method "Returns True if this connection is exist." "is exist" = "exists"?

In names method "...contains only names which is connected..." "...which are connected..."

In connected method "...If "name" is not exists in..." "...name does not exist in..."

Finally, Precondition "All data are correct" "All data is correct"

All the best,

Gus