Error code CS1612...

I'm getting an error cade at lines (7-9,36) about the fact that a field initializer cannot reference the nonstatic field, method, or property.
I tried to find the awnser over the internet but I tried everything but it all didn't work.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class PickUp : MonoBehaviour {
5.    
6.     // The variables for the positions.
7.     float CharacterPositionX = Character.transform.position.x + 3;
8.     float CharacterPositionY = Character.transform.position.y + 3;
9.     float CharacterPositionZ = Character.transform.position.z + 3;
10.  
11.     // The Player and the tagged objects.
12.     public GameObject CarryableObject;
13.     public GameObject Character;
14.  
15.     void Start() {
16.         // The origin of the objects.
17.         CarryableObject = GameObject.FindWithTag("Carryable");
18.         Character = GameObject.Find("Character");
19.         // The code for determining the position (Put in note mode to deactivate but keep it).
20.         // CharacterPositionX = Character.transform.position.x + 3;
21.         // CharacterPositionY = Character.transform.position.y + 3;
22.         // CharacterPositionZ = Character.transform.position.z + 3;
23.   }
24.    
25.     void OnTriggerStay(Collider other) {
26.         if(Input.GetKeyDown("e")) {
27.             // The position relative to the character.
28.         CarryableObject.transform.position.x = CharacterPositionX;
29.         CarryableObject.transform.position.y = CharacterPositionY;
30.         CarryableObject.transform.position.z = CharacterPositionZ;
31.         // The rotation relative to the character.
32.         CarryableObject.transform.rotation = Character.transform.rotation;
33.         // The gravity.
34.         other.attachedRigidbody.useGravity = false;
35.         }
36.     }
37. }

 

This should help:

https://support.unity3d.com/hc/en-us/articles/207079263-What-is-CS1612-