He thought I had tried to make a fool of him but no, I was really desperate to get him as my boyfriend.

make 在这里是动词，意思是"使成为"或"造成某种状态"。 a 是不定冠词，表示"一个"。 fool 是名词，意思是"傻瓜"或"出丑的人"。 of 是介词，表示所属关系或对象。 make a fool of 是一个固定短语，意思是"愚弄某人"或"让某人出丑"。