Increase speed when object hits collider ?

Hey everyone, I'm still learning Unity and C# and this is my first game I'm working on. Basically what I want is that once my plane hits a Box Collider, the scrolling speed of the background and the columns (obstacles that scroll as well) increases by a little bit.

Here's the Game Control code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 using UnityEngine.UI;
 
 public class GameControl : MonoBehaviour {
     public static GameControl instance;
     public GameObject gameOverText;
     public Text scoreText;
 public bool gameOver = false;
 public float speed = -5f;


 private int score = 0;

 // Use this for initialization
 void Awake () {
     if (instance == null) {
         instance = this; 
     } else if (instance != this) 
     {
         Destroy(gameObject);
     }
 }
 
 // Update is called once per frame
 void Update () {

     if (gameOver == true && Input.GetMouseButtonDown (0)) 
     {
         SceneManager.LoadScene (SceneManager.GetActiveScene ().buildIndex);
     }
 }

 public void PlaneScored()
 {
     if (gameOver)
     {
         return;
     }
     score++;
     scoreText.text = "Score: " + score.ToString ();
 }
 public void PlaneDied() 
 {
     gameOverText.SetActive (true);
     gameOver = true;
 }

}

And here's the code for the columns:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Column : MonoBehaviour {
 public GameControl control;




 private void OnTriggerEnter2D (Collider2D other)
 {
     if (other.GetComponent<plane> () != null) {
         GameControl.instance.PlaneScored ();

          }
 }

}

And finally the scrolling object code :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class ScrollingObject : MonoBehaviour {

 public GameControl control;
 private float speed = 0;
 private Rigidbody2D rb2d;


 // Use this for initialization
 void Start () {
     rb2d = GetComponent<Rigidbody2D> ();
     speed = control.speed;
     rb2d.velocity = new Vector2(speed,0);
 }
 
 // Update is called once per frame
 void Update () {

     speed = control.speed;
     rb2d.velocity = new Vector2(speed,0);


     if (GameControl.instance.gameOver == true) 
     {
         rb2d.velocity = Vector2.zero;
     }
         
 }

}

Any help is appreciated, thanks a lot !