Based on the Zeestyle theme, it just seems very dated.
There is a bunch of custom CSS that you could implement, but that would be challenging.
I would start with this plugin, and configure it – see if it helps:
WPtouch – Make your WordPress Website Mobile-Friendly – WordPress plugin | ww.wp.xz.cn English (Canada)
Your ZeeStyle theme is extremely outdated. According to the developer, it was retired in 2024. This means that there will be no further updates. Who knows how old the programming is.
Your theme is responsible for the frontend output. So, in addition to trying to solve the shortcomings with a plugin, you also have the option of choosing a current theme. There are thousands of free and up-to-date themes available.
Keep in mind that since your theme is very old, it may eventually become incompatible with WordPress or the PHP version set by your hosting provider. At that point, you will have to change the theme anyway.
Thank you @threadi and @corrinarusso for your help. I have downloaded the WPtouch Plugin for a short term fix and will plan in time next week to research and activate a new theme.
