Removing paragraph indentation, and removing page title.

Using the Constructor theme I’m building a site (https://www.greenmendo.org/) but I have a few questions I could use some help with:

1. How do I remove the indent before paragraphs like the one on the homepage that begins “Visitors may choose…”? I’m not using the <p> tags in the html so I don’t understand why I can’t get those to go away.
2. At the top of each page, in the main content area is a white box that says the name of the page. How can that be removed?
3. The text in the menu buttons are so small. How can I make those bigger?

I know these questions are probably novice, but I am a novice. I don’t know PHP. I very much appreciate any help with these questions, but if the answer involves PHP, would you explain it to me like I’m a 5th grader.

Thanks!