My son is 4 years of age. he has 4 rotten teeth mainly the central and lateral incisor. at what age do his name teeth start growing and would you advise me to have them removed?

Hard to say: The first teeth are important position holders for the adult teeth which will not emerge for a few more years. In the US we make every effort to restore /salvage these prominent teeth. Removal is a simplistic solution, but may lead to significant crowding when the permanent teeth begin to grow in. See a dentist and find out what your options are locally.