There are several ways to get the player.
Assuming single player, you can use for example:
#include "Kismet/GameplayStatics.h"
...
ASoccerGameCharacter* Player= Cast<ASoccerGameCharacter>(UGameplayStatics::GetPlayerCharacter(this, 0));
or
ASoccerGameCharacter* Player = Cast<ASoccerGameCharacter>(GetWorld()->GetFirstPlayerController()->GetPawn());