Zend certified PHP/Magento developer

encountered an issue where the modifications made to the style-m.css and style-l.css files are not being reflected on the website

After the installation of the Martfury Magento theme on my server, we attempted to make changes to these two files but were unable to locate them within the theme directory. I found these files in,

/pub/static/frontend/MageBig/martfury_layout01/en_US/css/styles-m.css
/pub/static/frontend/MageBig/martfury_layout01/en_US/css/styles-l.css

Unfortunately, the modifications made to these files have not been successfully reflected on my website. when I run static content deploy command the changes has gone.so, what I can do to save these changes permanantly to my website ?