Build me a App where you find friends

On the app i want you to be able to do the following:

Create a user account
Add friends
Post "activities" that people can join
Chat with your friends
Match with new friends (See people with same intrests and same friend groups etc)

I have a few ideas on how the app should look but something like: https://www.gofrendly.se/

I want the app for Apple and Android