my earlist memory is of when i was six, my sister was born. she was very small and cute.
↖ 연결부분이 어색해서요.
my most memorable teacher was mr.min from the _____ grade.
↖ 기수, 서수 상관없이 들어가도 되나요?
because he was very kind, and he was very nice to me.

she lived with her family in 서울.
she was very kind and she made me laugh.
we used to eat lunch together.

she is a freshman at seoul national university.

전체적으로 어법이 맞는지 좀 봐주세요. 과거, 현재, 전치사가 굉장히 민감해서요 ^^
이상한 부분이 있다면, 꼭 가르쳐주시고 고쳐주세요. ^^

그럼 좋은 하루되세요.