Why Sever hangs and give 504 Gateway Timeout?

I have created a video streaming site like udemy and uploaded that site in AWS with instance t3.small. Website videos are in 1080px.

But what actually happening right now is as soon as any video page loaded, sites go in 504 gateway error.

I am not getting any proper solution for this. Also, How I can manage video streaming in my server. My website is developed in Laravel and the frontend is in the blade.

via Chebli Mohamed