Here are the sentences with the mistakes underlined and corrected:

1. Emma has washed the dishes after dinner.
_(Correct: "washed" should be "has washed")_

2. Oh my god, I put too much salt into the soup.
_(Correct: "salts" should be "salt")_

3. My teacher was angry because some students did not do their homework.
_(Correct: "homeworks" should be "homework")_

4. It is very dangerous to play with knives.
_(Correct: "knifes" should be "knives")_

5. It took me around five to six hours to finish my job.
_(Correct: "hour" should be "hours")_

6. My daughter likes cheese very much.
_(Correct: "a cheese" should be removed)_

7. I asked my professor for advice on my career.
_(Correct: "a advice" should be "advice")_

8. On my way to the countryside, I saw some buffalo.
_(Correct: "some buffalo" is fine, but "buffalos" can also be used for plural.)_

9. There is only a few buses on the road today.
_(Correct: "a few" should be "few" and "bus" should be "buses".)_

10. Mr. John has three children, two boys and one girl.
_(Correct: "child" should be "children")_