Here are the sentences with mistakes underlined and corrected:

1. Emma **has** washed the dishes after dinner.
**Correction:** Emma **washed** the dishes after dinner.

2. Oh my god, I put too **much salt** into the soup.
**Correction:** Oh my god, I put too **much salt** into the soup. *(This is already correct; "salts" is incorrect when referring to salt in this context.)*

3. My teacher was angry because some students did not do their **homeworks**.
**Correction:** My teacher was angry because some students did not do their **homework**.

4. It is very dangerous to play with **knifes**.
**Correction:** It is very dangerous to play with **knives**.

5. It took me around five to six hours to finish my job.
**Correction:** It took me around five to six **hours** to finish my job.

6. My daughter likes a cheese very much.
**Correction:** My daughter likes **cheese** very much.

7. I asked my professor for **a** advice on my career.
**Correction:** I asked my professor for **advice** on my career. *(“Advice” is uncountable; “a” is unnecessary.)*

8. On my way to the countryside, I saw **some buffaloes**.
**Correction:** On my way to the countryside, I saw **some buffaloes**. *(Buffalo can be both singular and plural without changing form.)*

9. There is only a few **buses** on the road today.
**Correction:** There are only a few **buses** on the road today.

10. Mr. John has three children, two boys and one girl.
**Correction:** Mr. John has three children: two boys and one girl. *(Use a colon to introduce the list.)*