You may have messed up the partition table when you moved the leading edge of the partition, but hard to say. Moving partitions is always dangerous and moving the leading edges is the most dangerous. Probably why Disk Management will not let you do that.
Using the paperclip to attach a snipping tool picture of your disk management window will always help, guessing about a situation is not productive for any of us.
But maybe you need to look and see if GParted has an option to repair a partition, and it not, you might download
Partition Wizard, the Home bootable version to make a CD or USB Flash Drive, which is free. It does have an option to repair a partition and maybe you can get your second boot back. Since you did not...