1. He must have been a bully when he was a kid. 2. Her paintings are superb. [Correct] 3. She doesn't have a single clue about what he's saying. 4. My heart shattered when I realized we were leaving the country immediately. [Original was correct, but you'd hear this version more]

1. He must have been a bully when he was a kid. (''must be" is a conclusion about the present) 2. Her paintings are superb. (Yes!) 3. She doesn't have a single clue about what he's saying. (preposition. The question to "She doesn't have a single clue." is "About what?") 4. My heart shattered when I knew we were leaving the country immediately. (A suggestion: "My heart shattered the moment I knew..." "When" is OK, but a little bit simple.)

1. He must be a bully when he was a kid. "He must of been a bully when he was a kid" 2. Her paintings are superb. (Correct) 3. She doesn't have a single clue on what he's saying. (Correct) 4. My heart shattered when I knew we were leaving the country immediately. (Correct, but no offten said that way. When I hear it I feel like the immediately should be placed somewhere else or shouldn't be there, but it is correct)