1. Best of all, I can sing Korean pop songs with my friends.

Question

2. Most importantly, I can sing Korean pop song with my friends.

(Are both the same in meaning?)

3. I fougnt with Don badly.
4. I fought with Don teribly.
5. I fought with Donheavily.
6. I fought with Tom very much.

(Ae they all the same and grammatical?)

7. I was angry at Don.
8. i was angry with Don.
(Which preposition do we have to use?)

Answer 1

1. Best of all, I can sing Korean pop songs with my friends.

2. Most importantly, I can sing Korean pop song with my friends.

(Are both the same in meaning?)

3. I fougnt with Don badly.
4. I fought with Don terribly.
5. I fought with Don heavily.
6. I fought with Tom very much.

(Are they all the same and grammatical?)

7. I was angry at Don.
8. I was angry with Don.
(Which preposition do we have to use?)

Answer 2

Both 1 and 2 are the same and correct.

Put the modifiers of fought right after the verb. I fought badly - would mean that you were not a good fighter.

Did you mean that you had a bad ( terrible) fight? Then you need to say I had a terrible fight with Don.

Heavily would not be used.

"often" would be better than "very much".

7 and 8 are interchangeable.