What should I reply when my teacher say "I'm glad you....!" ?
I feel weird if I say thank you.....

Question

Answer

You're being praised. The proper response is Thank You.

Answer

You may say: I will work more hard.

Answer

You may not need to reply at all.  Your response depends on the context and who spoke first, you or the teacher.

Example 1:  (class activity has just completed; teacher speaks last)
You:  That was fun!
T:       I'm glad you enjoyed it.
(no reply is needed or appropriate)

Example 2:  (you arrive late to class due to very bad weather; teacher speaks first)
T:       I'm glad you arrived safely.
You:  Me too.  (or thanks)

Answer

A little more context would help, but I'll give it a try.

I'm glad you are enjoying learning English. Yes, I am enjoying it, thank you. (You could leave the "thank you" off but natives wouldn't)
I'm glad your house didn't get swept away in the flood. Thank you, I am too or I am too, thank you.
I'm glad you managed to show up for class on time. (weak smile as a reply)

Hope this helps.

Answer

you can always reply by a smile :pp

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