If someone could help me correct these HARD SENTENCES I'd be thankful

Could you please help me correct these sentences I find difficult?

1 You can't tell if I haven't done it.
2 It was either I arrived late or I didn't buy you it, so I decided to arrive on time.
3 Why work somewhere where you hate it./somewhere you hate./at/in/for a company you hate?
4 If you jump out of a moving train, once you hit the ground, you'll go flying in the direction in which the train is going.
5 In 5 minutes she'll be in the process of cooking us food.
6 Have you ever seen me pregnant?
7 The nerve is dead in my tooth which is why it no longer hurts.
8 What platform will the train pull into?
9 I leave in less/under an hour.
10 He said the people who said that died/would die.
11 His tooth is too set back from the rest.
12 What does a kid have to do for his parents to hate him/so his parents hate him.
13 Not to be a buzz kill, but can you turn the music down./I'm not trying to be a buzz kill but....
14 Once the first timer hits 0, the second timer starts counting down.
15 She has such little style/such ugly style.

Thank you