Where can I see the disk load level and how much percent is it occupied?

To control the load on the virtual server, including on the disk, you need to go to the control panel and select the necessary server, then open the Statistics tab:

Information about how much your server's files take up cannot be displayed in the control panel and it must be checked directly on the server. The fact is that we do not know and cannot know what is mounted in the partitions inside the server, which file system is used, and other similar things. The hypervisor does not have access to the mount points.