Is it normal that 3 years old child start to copy what other people does?

Yes, it is normal for a three-year old to imitate others. This is how toddlers pick up socializing skills and learn what are acceptable and unacceptable behaviour. A lot of my friends put their “copying behaviour” to good use. Such as asking them to help out around the house and involving them in dinner preparations. One key thing to note would be that parents and adults in the house must be on their “best behaviour” to be good role models for the children to learn from. ;)