Enhance Shopify Site with Key Functionalities

I have Recently got a shopify Website Done the Person who did it missed out on some key functionalities , the website is a B2 B website for a single Corporate its sole purpose is to facilitate its employees... (Budget: ₹1500 - ₹12500 INR, Jobs: API Integration, Backend Development, Database Management, HTML, PHP, Shopify, Shopify Development, Web Development, Website Design, Workflow Automation)