Maria,
The demo file cannot be uploaded on eGO forum. You need to upload that file on a file storage site and provide the reference link given to you on the Report a player form.
Here is step by step how to submit a request for leadership to look into extending or permanently banning a player.
Assuming you already have the player name, their Unique Steam ID and the demo .dem file:
1- Go to filedropper.com, upload the demo file and copy the link they provide you.
2- On eGO's forum home page on the very bottom there is a section titled
Administrative and. Under it you will see the Report a Player link.
3- Click that link and on the right side top of the Report a player page, click on Post thread.
4- Populate the form with the information you have and on line 7 where it says Demo Link, paste the link you copied from filedropper.com.
I offered to help you with this exact situation in a previous post and did not hear from you.
IMO, you should not vote ban another player for a violation that requires leadership intervention until you get these steps down.
And you can still contact me for further help on this or anything else you need help with.