我和一个同学周五下午散歩散了四十五分。 我妈妈游泳游得很好。 你见过一个汉语老师吗？ 他休息了多久了？

2 points 1. about tense 我早上吃了一个苹果 I had an apple this morning. ( simple past - I am telling you what did I eat this morning) 我早上吃了一个苹果了 (I have already eaten an apple this morning) ( present perfect - please don't push me to eat another one, I have had enough fruits for today) 2. 个/一个 Sometimes, 一 just can't be eliminated. If you are not very sure, just put a 一 before 个。 Have you ever met a Teacher. In English maybe you mean "have you ever met one or more than one Teacher" The main question is "have or have not" but not "one teacher or more teacher or none" So we could just ask "你以前见过汉语老师吗？" Another example 你病的很厉害，你去看医生了吗？ You are very ill, have you seen a doctor? It's very weird to say 你去看了一个医生吗？

1.虽然你用的语序没有错，但我们更习惯把时间状语放在句首 3.“这位汉语老师”通常是特指，也就是”the Chinese teacher”