Hi @Lie_Nuk,
Thanks for sharing this. One thing you may be able to do out of the box is use the Usage Statistics plugin - that does display some download statistics. You can read more about it in this thread: OJS 3 - Download statistics - #12 by bog
However, this might not be exactly what you’re looking for.
I’m not sure how exactly to go about getting this exactly the same, so I will ask some of my team members to comment when they are able to/available. You may wish to reach out to the developers of the site that you’d linked to to see if they are able to share their code - that might be a bit quicker.
Best regards,
Roger
PKP Team