Can someone help me with networking?

I try to make references/playercharacter, but they always fail.

Alright, not really sure what the problem is but you can try a few troubleshooting tips that work for me:

Check if the controller and controlled pawn are valid with an IsValid? node.

It works in singleplayer mode.

Same in the Anim_BP, it always fails.

Try this setup in your PlayerCharacter, it will not solve the problem but near down the solution by checking if the object is NULL or if its of another class:

Does the character get auto-possessed (controller defined in GameMode, Character Pawn settings in ClassDefaults) or do you active possess it with your Controller after spawning?

I use auto possess.