How to add Bump/Normal Map to surface shader? (CG)

Hi dear community. I am trying to get a normal map texture working with a custom terrain shader I got from following a tutorial series by Sebastian Lague. I have currently tried this:

   `Shader "Custom/Terrain" {
    Properties {
    // Textures and Scale-Slot
    testTexture("Texture", 2D) = "white"{}
    testScale("Scale", Float) = 1
    _NormalMap ("Normal Map", 2D) = "bump" {}
     }

    SubShader {
 Tags { "RenderType"="Opaque" }
 LOD 200

 // SHADER-Language = CG 

 CGPROGRAM
 // Physically based Standard lighting model, and enable shadows on all light types
 #pragma surface surf Standard fullforwardshadows

 // Use shader model 3.0 target, to get nicer looking lighting
 #pragma target 3.0

 const static int maxLayerCount = 8; // Max Amount of colors the terrain can have
 const static float epsilon = 1E-4; 

 int layerCount; 
 float3 baseColours[maxLayerCount]; 
 float baseStartHeights[maxLayerCount]; // ZONES FOR COLORS OF TERRAIN
 float baseBlends[maxLayerCount]; // BLENDS FoR COLORS/TEXTUREN
 float baseColourStrength[maxLayerCount];
 float baseTextureScales[maxLayerCount]; // Texture size
 float minHeight; //min. Hight of Map
 float maxHeight; //max. Hight of Map

 sampler2D testTexture; // Textur Slot
 float testScale; // Scale of the texture

 sampler2D _NormalMap;

 UNITY_DECLARE_TEX2DARRAY(baseTextures); // Texture-Array from TextureData(another Script) definieren

 struct Input {
     float3 worldPos; // Position on Map
     float3 worldNormal; // Normales of Map 
     float2 uv_Diffuse;
     INTERNAL_DATA
 };


 float inverseLerp(float a, float b, float value) // a = min.value, b = max.value, value = surrent value
 {  
    return saturate((value - a)/(b-a));
 }

 // --> TRIPLANAR MAPPING
 float3 triplanar (float3 worldPos, float scale, float3 blendAxes, int textureIndex)
 {
     float3 scaledWorldPos = worldPos/ scale;

     float3 xProjection = UNITY_SAMPLE_TEX2DARRAY(baseTextures, float3(scaledWorldPos.y,scaledWorldPos.z, textureIndex)) * blendAxes.x; 
     float3 yProjection = UNITY_SAMPLE_TEX2DARRAY(baseTextures, float3(scaledWorldPos.x,scaledWorldPos.z, textureIndex)) * blendAxes.y; 
     float3 zProjection = UNITY_SAMPLE_TEX2DARRAY(baseTextures, float3(scaledWorldPos.x,scaledWorldPos.y, textureIndex)) * blendAxes.z; 
     return xProjection + yProjection + zProjection; // Mix textures
 }

 // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
 // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
 // #pragma instancing_options assumeuniformscaling
 UNITY_INSTANCING_CBUFFER_START(Props)
     // put more per-instance properties here
 UNITY_INSTANCING_CBUFFER_END


 void surf (Input IN, inout SurfaceOutputStandard o) {


 float heightPercent = inverseLerp(minHeight, maxHeight, IN.worldPos.y);

 float3 blendAxes = abs(IN.worldNormal); 
 blendAxes /= blendAxes.x + blendAxes.y + blendAxes.z;  

     for (int i = 0; i < layerCount; i++)
     {

         float drawStrenght = inverseLerp(-baseBlends[i]/2 - epsilon, baseBlends[i]/2, heightPercent - baseStartHeights[i]); 

         float3 baseColour = baseColours[i] * baseColourStrength[i]; 
         // Textur
         float3 textureColour = triplanar(IN.worldPos, baseTextureScales[i], blendAxes, i) * (1-baseColourStrength[i]);

         o.Albedo = o.Albedo * (1 - drawStrenght) + (baseColour + textureColour) * drawStrenght;
         o.Normal = UnpackNormal( tex2D(_NormalMap, IN.uv_Diffuse));
     }

 }
 ENDCG
 }
 FallBack "Diffuse"}` 

This currently gets me to the point of having a black terrain (instead of the original triplanar mapped main texture) and looks like this:

This is the set up in the Unity inspector:

my question is: How can I achieve having the terrain with the bump map on it? Thx to everyone who helps out!