Explanation:

- My neighbour is: This phrase is grammatically correct, serving as the subject of the sentence.

- an young businessman: This part contains the error. "An" is used before vowel sounds, but "young" starts with a consonant sound. The correct form is "a young businessman."

- Who is very friendly: This part is correct. It uses a relative pronoun to provide more information about the subject.

- With everyone: This segment is correct, indicating interpersonal interactions.