I have an indepth knowledge of the drupal cms and what it means to work the drupal way, be it for drupal 7, 8 or 9.
To fix the responsiveness issue you may be having, depending on the version of drupal your website is built with, i may have to investigate the template/twig documents, the CSS document or any added js library loaded with your theme. You should have a fully functional and responsive website in less than 3 days depending on the complexity of your existing website.