website clean code

I am looking for an experienced and proficient programmer to clean up the code of my website. It is built in HTML5/CSS3, and I need help with code optimization to make sure it is up-to-date with the latest standards. I would like the code to be optimized to improve website performance, enhance website security, and make the code more readable and maintainable. My priority right now is to make sure that the code is valid html5 for better performance and functionality. Thank you for your help in advance!