If you can't delete the recovery partition in the application, then I recommend using a dedicated app that handles partitions very well. For example, install MiniTool Partition Wizard and then you can perform any operation you want on your hard disk. The software also supports dynamic disks, but that requires purchasing the Pro version. I have used the standard one and was able to do everything I wanted with the partitions.
Official website: http://www.partitionwizard.com/