у меня есть ошибки в коде, как их исправить?

Assets\Scripts\AllShapesJump.cs(8,34): error CS0027: Keyword 'this' is not available in the current context
Assets\Scripts\AllShapesJump.cs(8,108): error CS0119: 'Rigidbody2D' is a type, which is not valid in the given context

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class AllShapesJump : MonoBehaviour
{
    private int i = 0;
    private Rigidbody2D rbthis = gameObject.transform.GetChild(0).GetChild(0).gameObject.GetComponent(Rigidbody2D);

    public void ShapesJump() 
    {
        for (; i < transform.childCount; i++) 
        {
            if (Mathf.Abs(rbthis.velocity.y) < 0.05f)
            {
                rbthis.AddForce(new Vector2(Random.Range(-25f, 25f), 35f), ForceMode2D.Impulse);
            }
        }
    }
}