Answer:
I'm (useless at) sports.
I'm (involved in) organizing the charity match.
I'm (afraid of ) ghosts.
I'm (keen to) be a part of the volunteer group.
I'm (disappointed with) myself for not trying harder.
Step-by-step explanation:
Adjectives modify or describe the nouns while prepositions tell the position or relation of a noun or a pronoun with the other elements in a sentence. And an adjective + preposition is also known as adjective prepositional phrase.
Using an adjective + preposition to provide information about myself are as follows-
I'm useless at sports.
I'm involved in organizing the charity match.
I'm afraid of ghosts.
I'm keen to be a part of the volunteer group.
I'm disappointed with myself for not trying harder.
The words in bolded and italics are the adjectives + prepositions.