영어 문장 구조와 friendly interest 해석이 어려워요

“If we pay no attention to what the words say, however, and understand his meaning, we will return his gesture of friendly interest by showing equal friendliness, and in a short while he may be helping us to change the tire.”
문장 구조가 복잡해서 해석이 잘 안 돼요.
friendly interest에서 형용사가 연달아 쓰인 이유도 알려주세요.