Upgrade a code based web page

My custom-built website is live and running, but i need to enhance or add the function, I need a developer who can step in, audit the existing codebase, and deliver two concrete improvements:

• adding reservation page simply click to choose base, friendly screen in mobile display
• adding some statistics of attendance status
• users sometimes has failed in login, i believe due to chrome browser conflicts required cach cleared
• modernizing user profile page
• enhancing role function by level - admin/supervisor/user

You will be free to recommend the best approach or framework, provided it slots cleanly into the current stack and doesn’t break existing pages. Clear, well-commented code and a short hand-off document are part of the deal so I can maintain the features going forward.

If you have experience modernising customised sites and can turn these two upgrades around efficiently, let’s talk through the repo and timeline.