Java vs PHP for website( e-commerce website) for college project

I am a computer science student. I am working on a project. I would like to design such a website, in which people could visit from every corner of the country. I discovered something on the internet about this. I got some answer too but i am not satisfied with that.

Should be the feature of my website:-

1. The seller can do the registration via SMS or by visiting the website. (We assume that some sellers will not have a smartphone. In that case, the seller can register via SMS from a mobile)
2. The seller can upload their product details via SMS or by visiting the website.
3. The seller can view interested buyers.
4. Buyers can do the registration.
5. Buyers can view product details.
6. Buyers can chat with seller on the website. (The seller who does not have a smartphone, can reply message(SMS). Message(SMS) replied by the seller can be viewed on the website by the buyers)

Technology that i have to integrate into this project:-

Technology that can be used as a platform for connecting car buyer to Seller Domain Bucket - Agriculture, E-Commerce, Payment • Technology Bucket or Integration across systems – an Integration platform across systems with the security model for data extraction, SMS and Mobile Computing, Analytics & Data Science (if possible) - Big data/Hadoop, AI / ML, Data Aggregation, Visualization

Questions:-

1. How can i build a website.
2. Which programming language should i choose for the backend.
3. How to implement AI, ML etc in my project and for which purpose. eg. I want to use AI but for what?