do/ does is used in negative and interrogative sentences of simple present tense. eg. He does not eat apple. Do they go swimming. do/ does is used to emphasize something. eg. I do study English. do is used for 1 st and 2nd person while does is used for 3 rd person

you can increase your English knowledge by reading novel. It has been seen that Indian students find it more difficult to read novel of writer other than Indian . so if you have lack of interest in novel then you can start from short stories written by Indian writer and also most important thing, write the idiom, phrases, or word that you fail to understand and immediately clear it from your teacher,learn it on your tongue .so that you will be able to speak it fluently.

the formation is " what do you want" . it means that you are asking someone what one need from you.

I am not able to do this work.

it is not correct. the sentence is " we are among the world best friends.

second one is correct

No, but present perfect where has is used has essence of past.

at

I could go then I would go.

no