I started learning networking, but ran into a problem:
When I press the sprint button on Client, It changes the value of both players: Server and Client and it works only on Server.
Try to break the connection between the call of “ServerSprintStart” and the following Branch inside of SprintStart. Otherwise all the rest after “ServerSprintStart” will be executed even when you are Remote, but this has to be avoided if I got you right!?
In addition here is a good tutorial series on UE4 networking: - YouTube