Help with translation and rotation on a rigid body 2D

Hello everybody,

I know this is a problem that has already been mentioned several times on UA but I have already spent a lot of time looking for a solution and I really can't find it. For information, i am a 100% beginner in code and in Unity.

Basically, my game is a 2D platformer with horizontal scroll (player is a cube). Movements are quite simple:

• Player can fly (he's going up)

• Player can "drop" (going down)

• Player moves forward automatically

I added a rigid body on the player and I'm using gravity to go down. The rest is in the code below. I removed some parts that are not relevant for this but i can put the whole code if needed.

Everything was working fine until I tried to add some rotation to the player in order to give a real effect of flying when he's going up or of falling when he's going down. Cube seems to slow down a lot when rotating or after having rotated and it goes off the camera field. I tried Slerp, transform.Rotate(), AddTorque but I still have the same issue.

Here is the code for the player.

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class PlayerScript : MonoBehaviour
 {
     public GameControlScript control;                        // Reference to GameControlScript to get game speed
 
     // variables for player movements
     float speed;                                            // Game speed
     Rigidbody2D rigidBody;
     public FlyScript flyScript;
     float maxY;
 
     bool isMovingUp;
     bool isMovingDown;
     Vector3 LastPOS;
     Vector3 NextPOS;
 
 
 
     void Start()
     {
 
         rigidBody = GetComponent<Rigidbody2D>();
 
     } 
     
 
     void FixedUpdate()
     {
 
         // Player translates automatically in function of game's speed
             //` -> game speed is a float set in another script
         float speed = control.gameSpeed;
         transform.Translate(new Vector2(1, 0) * speed * Time.deltaTime);

 
         // if player press fly button, then we change rigidbody velocity and we decrease gravity effect
         if(flyScript.CanFly() )
         {
             rigidBody.velocity = new Vector2(0, 5);
             //Vector2 force = new Vector2(0, 5);
             //rigidBody.AddForce(force);
             rigidBody.gravityScale = 1;
         }
         // gravity is increased when user is not pressing fly button
         else
             rigidBody.gravityScale = 2;
     }
     
     // Part used for rotation. Not finished
     void LateUpdate()
     {
 
         
         NextPOS.y = transform.position.y;
 
         // if player is going up
         if(LastPOS.y < NextPOS.y)
         {
             isMovingUp = true;
             isMovingDown = false;
         }

             // if player is going down
         if(LastPOS.y > NextPOS.y)
         {
             isMovingDown = true;
             isMovingUp = false;
             //transform.rotation = Quaternion.Euler(0,0,45);
         }

             // if player is steady
         else if(LastPOS.y == NextPOS.y)
         {
             isMovingUp = false;
             isMovingDown = false;
         }
         
         LastPOS.y = NextPOS.y;
     }
     }

And here is the code for the camera

 using UnityEngine;
 using System.Collections;
 
 public class CameraScript : MonoBehaviour
 {
     // Reference to GameControlScript to get game speed
     public GameControlScript control;                            
 
     void Update ()
     {
         // Camera translates automatically in function of game speed
         float speed = control.gameSpeed;
         transform.Translate(Vector2.right * speed * Time.deltaTime);
     }
     } 

Maybe the problem doesn't come from the slerp or torque but from somewhere else in the code. I honestly don't know but if someone could help me out, that would be great.

Thanks!