So, after discussing with Berend, I figured out that I need to explain myself better and that is what I'm going to do.
So, my mission is to write a windows batch script that will:

1. **Display**(print to screen) the value of anyone from the environment variables I have(but maybe I need to check if it exists, and if not I need to create one? I'm not sure)
1.1 If I need to check if the variable exists, there is any if or for loop that I can do to check it?
If not, I think that I'll just create new environment variable and work with it.
2. I need to update the value of the previous variable I just printed.
3. Display the value of the current variable **After** the update I just did in step 2.

I hope now it's more clear than before and I'll be glad for any help.