Correct sentence is May i come in sir/madam? used when you enter in classroom/room/office. you are asking for permission.

feel surprise.

nothing much. what about you?

Have is used to show possession. example I have two hands. I have one child.

Example I was shocked when i heard about your accident or any bad news.

Something that join or connects

Harsh has submitted the book.

to make something less harmful/ unpleasant

Correct Would you like this app?

because in honest 'h' is silent. and after that character 'i' is vowel. hence an is used before honest.