How to properly expand a partition's size?

I have divided my 1000 GB or so hard drive into two parts, in order to install Ubuntu. However, System Monitor for some reason says I can only use 202 GB (and not about 500 GB as I would expect). The rest seems to be distributed somewhere else (like the image below).

I do not understand why it happens, but I just deleted my old Windows partition using the Live USB, and I want to relocate all the remaining space to Ubuntu, in order to use all of my hard drive there. How can I do this in GParted?

Edit: If I type sudo lsblk -f in the terminal in the main partition (not the USB), it gives me the following (egavs is my username):

NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
sda                                                      
├─sda1 ext3         ebee7c6e-b496-4156-96be-33babd8af832
├─sda2                      
├─sda5 ntfs         01D04ACDA066D7F0
├─sda6 ext4         f8ce9aa8-15fc-424c-b3ae-7162087664f5 /
└─sda7 swap         eb95af05-2b8b-47e8-abb7-7a7df5c556a6 [SWAP]
sdf                             
└─sdf1 vfat         7052-3404                            /media/egavs/7052-3404
sr0