Create a curve with the mouse at the apex of the curve ?

(For context: 2d plateformer game with a stone(projectile) that light up everything when shooted)

Hey so it's been a long time I wanted to do this, but I can't resolve it by myself so i'am asking all of you.

I want the to have the screen positon of the mouse to define the apex of the curve that will shoot a projectile.

So i've made this but impossible for me to do what I want... any Idea ?

 public float MouseX = 0f;
 public float MouseY = 0f;

 public Transform Heropos;

 private Camera _cam;

 public LineRenderer lr;

 void Start()
 {
     _cam = Camera.main;
 }

 public void Update()
 {
     Vector2 MousePosWorld = Camera.main.ScreenToWorldPoint(Input.mousePosition); //mouse world positon
     Vector2 MousePosScreen = Input.mousePosition; //mouse positon by the leftbottom of the screen
     transform.position = new Vector2(MousePosWorld.x, MousePosWorld.y);
     MouseX = (MousePosScreen.x + (_cam.pixelWidth / 2));  //find the center of screen  
     MouseY = (MousePosScreen.y -+(_cam.pixelHeight / 2)); // same

     Vector3 position = new Vector2(Heropos.position.x, Heropos.position.y);
     Vector3 velocity = new Vector2(MouseX, MouseY);
     
     List<Vector3> path = new List<Vector3>();

     float duration = 300f;
     float timestep = Time.fixedDeltaTime;
     for (float t = 0f; t < duration; t += timestep)
     {
         velocity += Physics.gravity * timestep;
         position += velocity * timestep;
         path.Add(position);
     }
     if (Time.timeScale == 1) 
     { 
         lr.positionCount = path.Count;
         lr.SetPositions(path.ToArray());
     }
 }

i've already a projectile behavior script and I think I just need the coordinates of my mouse to create a vector2 for it's velocity. (tell me if I'm wrong but that not what I want to be help with RN)

Thanks ya (And sorry for the bad english i'm not anglophone)