Hi,

What is the difference between professional and normal English? Please teach.

To express one self we can use formal language which is professional English.In a professional letter we address the person to whom we are writing to as "Dear Sir", but informal letter to a friend will be addressed as "Dear Monika".In order to express ourselves informally we may use slangs but never in formal letters.
Just like we will not be dressed in casual clothes for an interveiw we will also not talk /write in casual language in a formal/professional situation.

Normal english is in our daily day to day activities, whereas professional english is used in formal situations like office, fund raiser parties etc.