struggling with creation of my first theme

I’ve been trying to convert the html we have on the website for a charity I work with into a template so we can move to WordPress to run the website and dynamically update content as we go. I am a complete novice–self-taught–but despte that I’ve done alright. However, I’ve hit a snag and could use some help. I’ve attempted to mod the default template so it looks like the non-wordpress site. I’ve manage to get just about everything to work but there are some formatting and layout issues on the home page that are giving me grief. I’m sure this is a CSS issue but I’m new to CSS as well (like I said… total novice). Can someone give me a hand? The two sites are:

https://www.coloradohebrewchorale.org/ (this is the non-WP site)

and

https://chc.arielbenjamin.com/ (this is where I’ve been playing with making the switch)

The problems will be obvious when looking at the home page of the two sites (and I haven’t really migrated any of the other content yet… just getting the shell ready) and I’m hoping that to a more trained eye the solution will be as obvious. Thanks for your help!

Ariel