Reflecting a bullet doesn't work properly

I have a attackarea, in which i can attack and reflect bullets.
The problem is that the reflection doesn’t work properly.

Here’s a example how it looks:

I wan’t it to reflect it STRAIGHT BACK, not up or down.

These two script-parts are the only relevant for this function:

if (collider.tag == "bullet")
{
    Rigidbody2D rbOther = collider.GetComponent<Rigidbody2D>();
    if (rbOther != null)
    {
        Vector2 incomingVelocity = rbOther.velocity;
        Vector2 normal = (collider.transform.position - transform.position).normalized;
        Vector2 reflectedVelocity = Vector2.Reflect(incomingVelocity, normal);

        // Weise die reflektierte Velocity dem Rigidbody2D zu
        rbOther.velocity = reflectedVelocity;
    }
}
void Update()
{
    if (Input.GetKeyDown(KeyCode.G))
    {
        var bullet = Instantiate(bulletPrefab, bulletSpawnpoint.position, bulletSpawnpoint.rotation);
        bullet.GetComponent<Rigidbody2D>().velocity = bulletSpawnpoint.up * bulletSpeed;
    }
}