In search of incorrect sentences: Ten Examples.
I have to find two incorrect sentences among the following ten examples.
However, I think there is more than two that seem to be grammatically incorrect.
Could you possibly find all the incorrect sentences and correct them?
By the way, these examples were written by non-native English speaker.

1. I was ever been in Sydney.
2. John has broken the window.
3. We have washed our father's car.
4. Suzan has written a letter to her mother.
5. I have known him for almost three years already.
6. I looked myself in the mirror.
7. They loved themselves a lot.
8. Recycling is good for the environment.
9. I have been to South Korea yesterday.
10. You can prevent accidents by cleaning the snow.

Question

In search of incorrect sentences: Ten Examples.
I have to find two incorrect sentences among the following ten examples.
However, I think there is more than two that seem to be grammatically incorrect.
Could you possibly find all the incorrect sentences and correct them?
By the way, these examples were written by non-native English speaker.

1. I was ever been in Sydney.
2. John has broken the window.
3. We have washed our father's car.
4. Suzan has written a letter to her mother.
5. I have known him for almost three years already.
6. I looked myself in the mirror.
7. They loved themselves a lot.
8. Recycling is good for the environment.
9. I have been to South Korea yesterday.
10. You can prevent accidents by cleaning the snow.

Answer

1, 2, and 9 are grammatically incorrect.

Answer

#1 is definitely wrong. And there is no way to correct it without knowing what the speaker wants to express.

#9 is problematic  because when we use this particular construction, we don't usually mention a specific time in the past. So: "I was in South Korea yesterday."

#10 is grammatically correct, but "cleared" makes much more sense than "cleaned."

Some people find #6 to be wrong  but there is a lot of evidence for its use, and I can see how a mirror can refer to the eyes In a  kind of metaphoric sense. You are looking yourself in the eyes by means of the mirror. I  would not call this wrong, but I don't know if I would recommend it to learners.

See uses at https://www.google.com/search?q=%22I+looked+myself+in+the+mirror%22&hl=en-US&source=lnms&prmd=vi&tbm=bks&sa=X&ved=0CAsQ_AUoA2oVChMI8LaYmNKOxwIVRg2SCh1unQOe&biw=360&bih=484  or Google the sentence.

Answer

1 is incorrect. I'm not even sure what it means. It could mean:

a) I have never been in Sydney. (I've been in Melbourne, Canberra,, and Adelaide but I have never been in Sydney).

b) I was always in Sydney. (You thought I was in Melbourne last June, but I was always in Sydney).

6 is incorrect. It should be "I looked at myself in the mirror."

7 is perfectly correct English but it's a strange thing to say.

I think 10 is incorrect. It should be "You can prevent accidents by cleaning off the snow." or "by cleaning the snow off." It could be correct if it really means that it is the snow, itself, that should be cleaned. The problem is that I don't know how you would clean snow, and I don't know how dirty snow would cause accidents.

I think 9 is incorrect. "I was in South Korea yesterday" is correct English. "I went to South Korea yesterday" is correct English. "I have been to South Korea to visit Seoul" is correct English.

Answer

1. I was ever been in Sydney. -> I have been in Sydney.
6. I looked myself in the mirror. -> I looked AT myself in the mirror.

Most of these (#1,2,3,4,5, and 9) are testing your understanding of the present perfect tense (have + past participle). You can study the present perfect more if you're having trouble with these. Good luck!