Need help with speed increase(beginner level)

Hello. First post here. Non EN speaker,sorry.

Started my first project week ago( no exp with Unity or programing).

Simple game: items falls and you need to catch them with crate bellow.

I want to increase drop speed every 5 drops collected.



My script:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class DropMovement : MonoBehaviour
6. {
7.      
8.      float dropSpeed=2f;
9.    
10.      public ItemCollect instCollect;
11.        
12.     void Start()
13.     {
14.         instCollect=FindObjectOfType<ItemCollect>();
15.        
16.      }
17.  
18.    
19.     void Update()
20.     {
21.         transform.position = transform.position + new Vector3(0,-1,0)*dropSpeed*Time.deltaTime;
22.         transform.eulerAngles+=new Vector3(0,0,20f*Time.deltaTime);
23.  
24.             if(instCollect.countCheck==5)
25.          {
26.              dropSpeed++;
27.              instCollect.countCheck=0;
28.          
29.          }
30.        
31.     }

So,every time i collect 5 items,dropSpeed increases,but its back to 2f after I reach another number.
How can i save increased speed and not go back to default?

 

Got it. Fixed the post.