Thanks for the reply.
I have found this tutorial :
https://www.a2hosting.com/kb/developer-corner/linux/determining-high-disk-usage-locations
So I tried this command on the root :
sudo du -shc * | sort -h
It gave me good results, but I was wondering if there is any graphical alternative.
I also found this article :
Some of them have remote disk analyzer, but I don’t have any Linux system. I only have a win7, win10 computers and an android phone (I use my phone to administer the server using juicessh). So if any of these works, I may install a Linux VM.
And I don’t know if netdata or phpsysinfo or any other system app can help.