Hello,
Thank you so much for your reply.
As you can see the / partition is full and I want to add some space to it. In the Windows operating system, this can be done easily through a series of tools.

Have you read the other responses?

And using any linux distro you can do the same, just the exact name of the tools are different (but functionally more or less identical).

The / partition is full because you created it at an impractical size. I'm curious as to what Linux you are using that you would not expect problems with a / partition that small. There are tools to do this and you can enlarge the / partition and I gave a brief overview of that in my earlier post. I would again suggest that you start over and use more realistic sizes.

Your comment about windows only tells us you seem to be familiar with them but know little about Linux tools, pointless comment. Your problem is self created because you created partitions that were impractical for use. A little research prior to doing things often prevents problems such as this.

More likely the OP has a 10Gb VPS and mistakenly thought that would be enough for all the things they want to do.

"Anyone can make a mistake" during the original configuration of a system. Just as they can rely on a mechanical device that subsequently begins to fail. LVM provides an elegant solution to both, and it was very well-implemented, by those who obviously knew first-hand what needed to be done.

Hello,
So can't I resize the / partition?

Cheers.

Would be nice to look for the answer yourself. It is answered several times on several different sites.
In general you can resize whatever you want, if you have enough resources (disk space), and if you have the right software and knowledge.
But you cannot resize the root partition of a running OS.
It looks like you did the setup/install in an impractical way, you are now stuck. You need to learn how can you resize it, it will take several steps (see for example post #11). But we cannot resize it for you.

In principle you can enlarge the root partition of a running OS.
But either you need the free space (sectors) immediately after it, or you need LVM to grow it with a not adjacent space.

Resizing the partition is possible but it is not likely that you will be able to do it until you do some research and learn from it. I gave you a basic outline of what you need in my earlier post (12) and you have been given other suggestions in other posts so what effort have you made. Many members here could do what you want but they had to learn it. To get a basic idea of what you need to know, look at the fdisk output and the sectors, beginning and end sectors for each partition. You will need some familiarity with fdisk or parted/gparted. Gparted would probably be easier to use for you and there is a detailed, online manual

Simple research probably could have prevented a 'mistake' like this. I expect the OP could install TinyCore or Slitaz on that virtual machine but not any standard Linux. That is why I suggested the simplest solution for the OP would be to reinstall with more appropriate sizes for whichever Linux s/he might be installing

Have you at least looked for an excessive number of log files under /var/log? That's an easy fix to get "/" down from 100%. Move a large one out of the log directory (temporarily moved into /home, perhaps) and begin compressing any older log files---then move the one you relocated to /home back and compress it if possible. "logrotate" will help to minimize the impact of log files once you've configured it to automatically compress logs and remove older ones that you may no longer need to retain.

HTH...