At this stage, your child is going to school and is learning a second language as well. In India, English is considered a second language. He will interact with peers and others in school and so will be able to translate well in his mother tongue.
What you need to know:
Your child now is going to school and interacting with his friends, teachers in his mother tongue or his regional language. So, he understand the language well. English medium schools are a prerequisite so he understand it too. With more complex brain development he is able to convert those ideas into his mother tongue and can translate some simple sentences like 'Who am I?' 'What is your name?' and various other simple sentences into his mother tongue.