Hey, me and a friend of mine wanted to speedrun Minecraft in coop. We looked on Youtube to maybe find a good explaination of how to play in coop in Java, but after trying everything, we still don't know how to join each other. It would be VERY appreciated if you'll could help us since we have tried almost everything. Thank you:)

You need to either be on a server or realm, or alternatively if you are on the same wifi, you could play on lan.

There is a very awesome method that uses the Lan feature to port to a server. Follow this tutorial and you should be good to go