( English teacher )
1. Your English is correct here, but if you are asking them after you have
taught a certain topic, it is better to ask : "Do you understand the topic now
2. It is better to say : "Those who still don't understand the topic,
please put your hands up." "For" is not the right word there and you don't say
"put up something" but "put something up" if you mean "raise it".
3. You must use the present perfect tense here, because you are asking about
a completed task. So, use "Have you finished already ?" However, "already' is
only used in this position to show surprise that someone has done something more
quickly than expected. If you are not surprised, just ask " "Have you finished
4.You should say : "Do you need me to explain this in Malay ?" "Explain is a
transitive verb and needs an object ( e.g. "this" ). In this situation, it is
enough to say "Malay" to refer to the Malay language, just as "English" is often
used to refer to the English language.