Hi FoxyFox06,
Have you tried the CHKDSK tool? Open CMD as administrator and run CHKDSK /R C: to see if it can fix the problem.
Not sure where your C and D drives are located, but Disk Management cannot shrink a partition and add the disk space to another partition because on basic disks the unallocated disk space can only be added to the partition left to it. You need to use some 3rd party tool to achieve that.