"She has studied English for three months." Correct "I have met many people in the class." "I met many people in the class" No, the meaning is not the same. With the first (present perfect), the 'class' has relevance to you NOW. You are either still going to the class, or only just finished and it is still in your mind. With the 2nd, the class you are talking about is in the past. "He likes learning English, When he was young,his father found a teacher to taught his brothers and his English,but when he moved to another city, his father didn’t find anyone." Correction: "He likes learning English. When he was young, his father found a teacher to teach his brothers and himself English. However, when he moved to another city, his father couldn't find anyone."

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One correction “taught his brothers and him ...”.