Changes to theme files or ninja forms not affecting published website.

Here are a few predicaments I am having with WordPress I don’t know if these problems are related:

1. I need to change my theme files a little bit, however, when I make the changes and press update on the theme files, the changes I make are not reflected on the actual published website.
2. I need to change some text on a banner, but when I change the banner text 
3. I have used ninja forms on my website. The Ninja Forms that I have made in the past remain visible and working on the site. However I have made new pages and want to add more ninja forms. When I add any ninja form it shows up in the block editor, but does not appear on the published website. It doesn’t matter whether I am using ninja forms that are used elsewhere and still work or not, but any ninja form now added to my website does not show up i the published website.

A few other clues that might be helpful:

• I am using a theme created by the small company that created my website.
• Other changes to my website seem to work. I can make new pages, I can add text and images to those pages.
• I dealt with any problems that could be related to caching both from my website and from the browser I was viewing the website on.