I searched a lot about multiplayer on Unreal but it’s very confusing. I would like to know how to implement multiplayer mode with servers (AWS) for example. In blueprint. No local servers (I think LAN is spoken), I want multiplayers for people from around the world to play with other people.
Hi there. What you’re going to want to look into is setting up a Dedicated server. As it for being confusing, multiplayer in unreal will do that to you. 
But the documentation I’ve linked should get you started. It also wouldn’t hurt to take a look at the replication documentation. For the most part, characters should replicate fine if your setup is similar to epics, but for everything else, you’re likely going to have to set up events to run server side (ie projectiles) to get those to replicateto clients. Good luck!