Dropdown menu, excerpt of post & follow button

Hi!

First, I would like to say that the Scrappy theme is really nice and is so me. (We need more feminine-looking themes!) Thanks, Caroline.

Next, I’m a major newbie in WordPress and quite ignorant about code. So here are my questions:
1. How do you add a dropdown menu on those main menu things on top?

2. How do you make the post on the homepage just an excerpt and not the whole post? I tried selecting that option in the Settings (Reading) that said “Summary” but it doesn’t seem to be working. And would that automatically have “Read more”?

3. How do I put some kind of follow button where people can put in their email to be notified that I have a new post?

My site is https://www.citygirlcountryhome.com

I’d really appreciate your help (Help! Been stuck.). Thanksamucho!