Small formatting problems integrating WordPress with an existing site

My objective: to integrate my WordPress blog with my business website.
I merged my site’s content with my WordPress blog’s files: style.css, header.php, footer.php, index.php. I created a blog.css. I was instructed to do this by an article I read on the subject. The result was that my WordPress blog page looks almost the way I want it to look. Can someone help me solve small formatting problems to help me complete the task? The header image is out of alignment with the nav bar, bullets don’t appear correctly on the nav bar, text on the nav bar is also out of alignment. Here’s a link to my WP blog: https://garykrupacpa.com/wordpress. I’m not familiar with PHP, which may be why I’m having these problems. I’d also appreciate if you’d recommend a good guide or tutorial on embedding WordPress in another website.