While first two screenshots are fine, third one presenting script should be posted using code tag.
See ** Using code tags properly .**
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class NewBehaviourScript : MonoBehaviour
{
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
}
}
Did you drag drop your new script onto Camera object yes?
Does it happens with any new script, as you created?
Does doble click on red error, navigates you anywhere?
Please copy paste full error here.
Did you try create new project again? Maybe current is corrupted somehow?
If so, do you have any previous version of Unity to try / test (i.e. 2018.3)?
Sorry, it is not obvious directly for me, what may be wrong. 