I don't know how to write my second paragraph about how Lord Capulet is presented from the beginning to Act 3 Scene 5

It is difficult to suggest an idea for a second paragraph without knowing what your thesis is. Yet, looking at how Capulet behaves in the earlier parts of the play, I can suggest several quotes that show a specific character trait that may lead you in the right direction.
One trait that Lord Capulet keeps at the beginning of the play is a sense of rationalism. For example, even though there is a family feud going on, he seems to have no grievances with Romeo himself. In fact, he seems to appreciate Romeo's character. When Tybalt recognizes Romeo at the Capulet Ball, his first reaction is to fight and kill him. Yet, Lord Capulet says to him,

Content thee, gentle coz. Let him alone.He bears him like a portly gentleman,And, to say truth, Verona brags of himTo be a virtuous and well-governed youth (1.5.74-77).

Lord Capulet bears no contempt for Romeo and appears by consequence to be a relatively level-headed fellow. While, at the beginning of the play, Lord Capulet wants to scrap with Lord Montague like a rowdy teenager, he quickly acknowledges his age and decides fighting to be inappropriate. Yet again, this shows Lord Capulet to be rational.
Taking an entire paragraph to sketch out this particular trait could help you make a convincing sketch of how Lord Capulet behaves in the first act.
http://2013.playingshakespeare.org/characters/lord-capulet.html

https://www.thoughtco.com/write-an-argument-essay-1856986