VPS disk space issue

Yes, i am using mysql and size of mysql folder of all databases is about 10gb

 

I second this information. Based on how the master node is configured, there is a chance that you may be seeing the disk usage for the entire Master Node, as opposed to your own container. I would open a ticket with your provider and show them the information, and ask them if they can look into the issue. While doing that, you can still look into resolving the issue, but based on the results of you running the following...

cd /
du -sh *

it looks like you are not using that disk space.

One last thought. Based on the fact that your disk sizes seem to be "stuck", another thing that I have seen, is if the master node has run out of disk space before. As it is a VPS, you are likely on a shared hosting environment like OpenVZ. As such, the disk may have been oversold, and filled up. Once filled, the disk can be cleaned up, but the correct disk sizes may no longer report accurately until a reboot is made on the master node, so you may be trying to resolve a problem that is out of your control. But, you may make a suggestion to the hosting provider regarding that, if nothing else resolves the issue.