6. She said that the pain was so intense she couldn't even budge (it seems to me that this is an inappropriate verb here, what can i substitute it for?) her feet.
I'd use 'move'.
7. The weather conditions were very harsh! I've no idea why Derrick couldn't understand that we just couldn't work in such intense heat.
I wouldn't use the exclamation mark here- it seems a bit of an anti-climax as the sentence isn't that emphatic.
8. It concerns me that hardly anyone is now ready to take care of nature. The only thing we're doing is inflicting damage on nature.
I'd use 'the environment'
10. The kids were behaving noticeably better that afternoon. What was the reason? (can I put 'for it' at the end?) If you like
12. Do you really want to spook Jim out again? How are you going to do it? Are you going to phone him again threatening to bomb his house when he's in? (perhaps, spook out isn't the best verb I can use, is it?) It's OK, but I wouldn't say 'when he's in' as there's not that much point leaving a bomb scare message on an answerphone.
