As Stated, we wanted to see if the C: and D: drives were separate disks or if they were on the same disk.
Also to see if there was any Unallocated Space to the Right of the C: Drive.
C: and D: are separate disks, there is no extra Unallocated Space to the Right of the C: drive.
You have a relatively small disk for your C: drive (ie) 120 GB total space.
In Disk Management, right click the Schijf 1 (Disk 1) and choose Properties.
This should tell you if this is a standard HDD or if it is an SSD.
The easiest thing to do is to upgrade your disk to a larger one, (ie) 1TB or larger, cloning your old disk to the new one, then removing the old disk and booting from the new C: drive disk.
If that is not possible, you can Move your C:\Users\UserName folders, (ie) Downloads, Documents, Desktop, Pictures etc to a your D: drive using the Location tab in the Properties of each folder. There is a tutorial in the Tutorials section of this forum. If you decide to do this, It is a little tricky and have to follow the instructions or things can get messed up. But this is just a band aid, you need a much larger disk.
Before doing any more surgery, it is suggested to make an Image file of your Schijf 1 using 3rd party Imaging/Cloning software and saving it to your D: drive or better yet an external USB HDD. You can also use this image to restore to a much bigger drive instead of cloning the old disk..