I'm sure it's won't be difficult for him to learn English but it will take time. Also teachers should always be observant because we've some children who doesn't understand anything the teachers are teaching them but when the teachers observe those students and try to be patient and try to make them understand by doing so it won't be difficult for those students again. And I'm glad you're always friendly and jovial with your students because students love teachers who are always jovial and friendly that's why you will see some students scoring lot of marks in the teacher who's always laughing with them than the other teachers.