I am looking for a Friend of mine an Englishman

People who speak french, want to learn English.

  There is a great book called "Le nouvell anglais sans peine" for those who want to learn English.

which sentence is correct? please comment according to the English grammar rules. 1- Where exactly do you live? 2- Where do you exactly live? 3- Where do you live, exactly? Thank you in advance.

Why we don't use "to teach" instead "to teaching" Why we don't use "to teach" instead "to teaching" I am looking forward to teaching you over the nex six weeks.

Singular and plural Ten dollars is a high price to pay. The word "is" Is it connected with "Sum" / sum=ten dollars. It's why we used "is" because "Sum = singular". Two and two is four. The word "is" Is it connected with the "Result" 2+2=4 / Two and two is the result. I can't see clearly please could you explain and comment.

Do these senteces all mean the same thing? please comment. London is the city in it Paul was born. London is the city in which paul was born. London is the city where Paul was born.

Modal verb and auxiliary what is the difference between modal and auxiliary? Thank you

could you please comment and explain more the gramaticul function of each of the sentence What caused him to change his mind? I think: What is question word subject of the verb cause, and him is the object (please explain more). But what about (to change his mind.

what is the difference between the two sentences 1- You didn't need to take a taxi. 2- You needn't have taken a taxi. and what are their tenses? Thanks to all of you