1. Yes, you can change the sentence from the first one to the second one: - "I had a friend who was a teacher in a private institute from the USA" - "I had a friend from the USA who was a teacher in a private institute." Both versions are grammatically correct and convey the same meaning. The second version simply places more emphasis on the friend being from the USA. 2. "Korean foods" is correct. When referring to types or varieties of food in general, we use the plural form. Therefore, saying "Korean foods" is appropriate because it indicates different dishes or types of food that are Korean and can vary in spiciness. So, your corrected sentence would be: "Korean foods are mostly spicy and they can be distinguished by the degree of spiciness." Not related but related, I love Kim chi!

Both sentences are correct, however they have slightly different meanings. When you say “I have a friend from the USA…” you are specifically giving information about your friend’s place of origin. In this scenario the private institution may or may not be in the USA. When you say “at a private institution in the USA” you are specifically giving information about the location where your friend teaches. Your friend may or may not be from the USA. Regarding your other question, you would need to change “spicy” to “spiciness”, because you need a noun rather than an adjective in that context.