Create a chat application; kinda replica for whatsapp.
Sing in using phone number, OTP auth.
Focus on UI, intuititve.
Maintain a universal contact list for all users.
Integrate a chat-bot as a user - user can chat with it.
Save chats for each user.
Rest upto imagination.
OpenAI, FastAPI, langChain etc. can also be used.
4-5 working days.