Fixed combinations: afraid of, good at, interested in, proud of
Be + adjective + preposition + noun/-ing
Be + not + adjective + preposition
Be + subject + adjective + preposition...?
💡 These are fixed combinations that must be memorized.
✓I'm interested in learning English.
✗I'm interested to learn English.
Interested takes 'in', not 'to'.
✓She's good at playing piano.
✗She's good in playing piano.
Good takes 'at' for skills.
✓He's afraid of flying.
✗He's afraid from flying.
Afraid takes 'of'.