The picture shows that the occupation of disk C is still within the normal range. If you want to expand drive C, you can have a partition assistant.

Select another partition with free space behind drive C, right-click the shortcut menu on the partition and select the "Move/Adjust Partition" option.

Drag the ball to leave an "unallocated space" in front of the partition.

When the adjacent position of drive C releases unallocated space, you can use the function of "adjust/move partition" to expand drive C. If the unallocated space is not adjacent, you can also use the function of "merge partition" to merge drive C and the unallocated space that is not adjacent.

Click OK to return to the main interface. Here, on the top toolbar, click the Submit button to submit the validity of this partition operation.