I know almost the basics of every subject including business, data science, psychology, and so on. How can I use all my knowledge into actions?

 Its great that you know so many subjects. For it to be more fruitful, you should also be willing to telescope in and out into different subjects and do more research if needed. With that rerequisite, you could go into crowdsourced problem solving.

e.g Eli Lilly has an open Innovation Challenge.

4 Amazing Crowdsourcing Competitions that Transformed the Industry 

Kaggle seems to be a good one for you, since you know data science. You can also go into user discovery study for startups.