If you get the error
Can not find include file Landscape.h in C++ it means you need to add Landscape to your Build.cs file.
Like mygame.Build.cs
// Fill out your copyright notice in the Description page of Project Settings.
using UnrealBuildTool;
public class mygame: ModuleRules
{
public tdl(TargetInfo Target)
{
PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "AIModule" });
PrivateDependencyModuleNames.AddRange(new string[] { });
PublicDependencyModuleNames.AddRange(new string[] {
"OnlineSubsystem",
"OnlineSubsystemUtils",
"Landscape",
"Steamworks"
});
DynamicallyLoadedModuleNames.Add("OnlineSubsystemSteam");
}
}