The data could be deleted if I move a partition?

When you resize partitions (such as shrinking D and extending C), your existing data on both partitions remains intact if the process is performed correctly. The goal is to only resize the partitions without deleting any data.

Simply moving a partition's location on the disk (like changing its position in the disk layout) can be risky, but resizing or shrinking one partition and then expanding another is a different process.