Partitions you want to resize must be adjacent to unallocated space in order for the resize to work. I don't think you can move unallocated space, so you would need to move the sda1 partition next to the unallocated partition.
Unfortunately, since sda1 is the boot sector you will likely not be able to boot after you do this. You certainly can do this, but you will need to repair the boot sector, which is another issue (see http://gparted.sourceforge.net/faq.php#faq-6).
Also, the 5.59GB unallocated space is within an extended(logical) partition, so if you want to add that space to sda1, you will need to resize the sda2 extended partition to be 5.59GB smaller.