"We chat" is just to combination of multiple apps. There are many apps with similar concepts like messenger apps. You hardly find any uniqueness in Skype, WhatsApp, Viber and signal etc. but all are successful and have billions of users. They all trying to solve same problem with similar solutions. The only difference you find is UI design and some minor things. Similarly, Udemy, LinkedIn learning, Lynda and Edx offers almost same services. Do we need to find problem or can we solve same problem which is being resolved by competitors?
It doesn't have to be an unsolved problem, you don't have to be the first - you just have to find your niche. It's the old "build a better mousetrap". Can you find a way to win customers that might have some unmet requirement, even if it's just UI or a slightly better customer service line, or some kind of peer effect i.e. all their friends have it?
I've worked with entrepreneurs who tried to develop apps or products that were trying to improve on existing competitors. What we found is that the earlier products didn't define their market well, or that younger customers preferred something a bit more friendly, e.g. Paypal vs. Venmo.
If you'd like more ideas on how to get to your MVP, feel free to message and we an set up a call.