GParted can't resize partition, but unallocated partition is available
Partitions need to be exactly above or below the unallocated space to get resized. Here you can extend only sda15, sda5, sda8, sda9 & sda10 partitions. Moreover unlike Windows Ubuntu can't work on dynamic disks, so it is impossible to extend the partition using the partition which is very far.
You need to move the existing partitions so that the unallocated space that you wish to use is adjacent to the target partition. See: https://gparted.org/display-doc.php%3Fname%3Dhelp-manual#gparted-resize-partition