1. Let's play football. (Let's + Infinitive) A Grammar mistake.
2. Why don't you get him a book? (Present Simple, interrogative form. Wh- question + auxiliary verb + subject + infinitive verb + Object or Complement in a sentence) A Grammar mistake.
3. She likes to draw pictures. (Like and draw are two verbs, you need TO to separate them) A Grammar mistake.
4. He likes riding bikes. (Wrong verb: you say 'ride a bike' or 'read a book') A Grammar mistake or could be spelling too.
5. I don't want to buy football boots. (Sound the same bye and buy /baɪ/) But one is a greeting and the other a verb. (Wrong Word)
6. What about going to bed early. (Wrong word- Wrong use of Wh- Questions)
7. He doesn't know which radio to buy. (Wrong Word- Wrong use of Wh- Questions)
8. We make footprints with our feet. (footprints/foot) (Wrong Word)
9. The computer is too expensive for me to buy. (Spelling mistake)
10. It's an enjoyable book about travelling. (I need an adjective: enjoyable, and enjoying is a verb)
I hope it helps.