Please correct these sentences please
1_你想想才买吧。（I want answer this sentence by 才）
如果已经买了，才表达的是说话的人在询问“你是经过考虑之后买的吧？”
如果还没有买，才应该更换为再“更”合适，你想想再买吧，表达的是说话的人在给你建议，希望你多考虑一下之后再决定买不买
2_你的病还没有好，病好了以后才上课吧。
这里的才应该更换为“再”
3_昨天我很不舒服，八点才睡觉了。（I want to answer this sentence by 才）
这里的才应该更换为“就”，意思是很早就休息了
4_听了我的话，就玛丽很快不哭了。
这里应该去掉“就”，或者把“就”放在很快后面：玛丽很快就不哭了
5_到中国以后，这个电影我再看了一遍。
这句话也可以这么说，如果把再更换为“又”更好
6_今年九月，她再来中国了。
这句话可能有两种意思：
1、九月还没有到，她还没有来中国，可以说“今年九月，她会再来中国”
2、九月已经过去了，她已经来中国了，可以说“今年九月，她又来中国了”，或者“今年九月，她再次来中国了”
“了”表示已经完成
Please correct these sentences please
3_昨天我很不舒服，八点才睡觉了。（I want to answer this sentence by 才）
才八点就睡了, I think 才 in this case is also different from 八点才睡 。
才八点就睡了 means sleep early, 八点才睡 means sleep late. So I think 才八点 means unexpect time, 就睡了 means sleep early.
e.g.
才三岁她就会弹钢琴了，unexpect age.
（这只西瓜）才一块钱他就卖了，unexpect price.
Please correct these sentences please
1_你想想才买吧。（I want answer this sentence by 才）
Google gives no idea about 才 in this case, in my apinion, 才 in this sentence is more like the character “再”, it used for contact two verb. A bit Likes the word "after", "You'd better buy it after thinking clearly."
3_昨天我很不舒服，八点才睡觉了。（I want to answer this sentence by 才）
This sentence seems incorrect.
The correct way is :
昨天我很不舒服，八点才睡。（means sleep late）
昨天我很不舒服，才八点就睡了。(means sleep early)
才 means 刚刚，八点才睡 or 才八点就睡了 means sleep at eight.
But I'm unsatisfied with this answer from google, especially the second sentence, it also can translate to "sleep at eight" when you remove the character 才，so I think 才 in this the second has someother use, I'd like to show you this case in English.
case 1:
Wonderful day!
八点就睡了。
case 2:
What a wonderful day!
才八点就睡了。
And in the first sentence, 八点刚睡 also is not equal to 八点才睡。When someone says 八点刚睡 or 八点睡的，he probabily think he sleep at the right time; When he says 八点就睡了，he probabily means he sleep too early; When he said 八点才睡的, he should considers sleeping too late.
