Why isnt my code working? C# [NOOB]

I need to know why my code is not working:

 using UnityEngine;
 using System.Collections;
 
 public class ShipController : MonoBehaviour{
 
     public float turnspeed = 5f;
     public float speed = 5f;
     public float trueSpeed = 0f;
     public float strafeSpeed = 5f;
     
     void Update () {
         
         float roll = Input.GetAxis ("Roll");
         float pitch = Input.GetAxis ("Pitch");
         float yaw = Input.GetAxis ("Yaw");
         float strafe = Vector3 (Input.GetAxis ("Horizontal") * strafeSpeed * Time.deltaTime, Input.GetAxis ("Vertical") * strafeSpeed * Time.deltaTime, 0);
         
         float power = Input.GetAxis ("Power");
         
         if (trueSpeed < 10f && trueSpeed > -3f) {
             trueSpeed += power;
         }
         if (trueSpeed > 10f) {
             trueSpeed = 9.99f;    
         }
         if (trueSpeed < -3f) {
             trueSpeed = -2.99f;    
         }
         if (Input.GetKey ("backspace")) {
             trueSpeed = 0;
         }
         
         rigidbody.AddRelativeTorque (pitch * turnspeed * Time.deltaTime, yaw * turnspeed * Time.deltaTime, roll * turnspeed * Time.deltaTime);
         rigidbody.AddRelativeForce (0f, 0f, trueSpeed * speed * Time.deltaTime);
         rigidbody.AddRelativeForce (strafe);
     }
 }

Errors:

Assets/ShipController.cs(16,32): error CS0119: Expression denotes a type', where a variable', value' or method group' was expected

Assets/ShipController.cs(35,27): error CS1502: The best overloaded method match for UnityEngine.Rigidbody.AddRelativeForce(UnityEngine.Vector3)' has some invalid arguments Assets/ShipController.cs(35,27): error CS1503: Argument #1' cannot convert float' expression to type UnityEngine.Vector3'