Which framework/library is best for website + mobile app based on javascript

Hi Im planning to create website with mobile app. Can you recommend me best possible framework/library based on javascript for it?

main requirements: - 2 languages - from 100-500 entries each one will have some basic information about it, location and photo

Aditional info: in my new part-time job I will have to learn ReactJs and for my engineers degree I will be creating mobile app in React Native.

Also do I need to buy database or is there some free option for creating databases. Until now I was using school database.