Are these sentence correct grammatically? Arad

1. 你改了！你做了什么？ Do you mean 'You change (sth.)' or 'You are changed'
2. 我等你在路口！你是在哪里？ 我在路口等你！In a Chinese sentence, the clause is usually ahead of the predicate or you can separate it into two parts like'我等你,在路口！' Grammarly, the aft half is correct. But we usually put '是' ahead of a verb as an emphasis. And you know, Chinese grammar cannot indicate the tense, we usually say '你现在在哪里?'.

3. 你后悔什么？
4. 你理解我的说吗？ It should be changed to '说的'.
5. 你几点放学？
6. 这帽子是放心吗？
7. 家具放在哪儿？
8. 你要参观谁？ '参观' usually means visit some places like museum or tourist attractions. We use '拜访'(formal) or '见'(informal) to represent 'to visit someone'.
9. 为什么这里是乱七八糟？ '是' is usually omitted here. I don't know the reason.

10. 我找到出可是没找你！你是在哪里？ '出' is a verb which means 'to exit' and '出口' is a noun means 'exit'.
11. 请给我杯子水！好吗？ 请给我(一)杯水,好吗？ (a) cup of water
12. 为什么你推我？
13. 怎么买飞机票？
14. 现在你愿意做什么？
15. 为什么你的手是在你的口袋？'是' should be omitted, see No.2.