I see the following on the Google Search Console. The following issues were found on your site:
How can I solve this?
Are you using a CMS (e.g. WordPress, Joomla, and so on) or an HTML template?
I'm using a free WordPress theme.
The best approach would be to contact the author of the theme. The author of the theme should be able to improve it for mobile usage in the following patches.
Alternatively, you can reach out to a third-party web developer to have it fixed for you.