let me see if I can help you. First you need to know something about LiveCD and GParted.
When using the LiveCD/LiveDVD/LiveUSB, GParted will be installed by default, so there is no need to install it in the Live Medium. This is different if you are using an installed version of Ubuntu in which GParted will not be installed by default, so you can only use GParted right away from the Live Medium but you need to install it in Ubuntu if you are running Ubuntu from an already installed scenario.
With this in mind, run the LiveCD/USB of Ubuntu and open GParted. I assume you read the Using GParted to remove windows partition on how to resize (Dragging the yellow bar for example). What we do now is, in your case, select the Locked partition inside the Extended partition (in your case sda5) as shown by the Gray KEY icon. Right click on it and select Unmount, Disable or any other option that appears that unlocks it.
After that, simply select the Extended Partition, right click on it and select Resize. you should be able to resize it this time.
I have made a video to help you along the way: https://www.youtube.com/watch?v=v1uPH2zgrxw
Looking at your EDIT 5, here are the steps you need to do to remove Windows 7 and be able to boot afterwards:
Delete the SDA1 partition and set the SDA5 to boot with the boot flag parameter
Boot from a Live CD and run boot repair as mentioned in Installing Ubuntu Alongside a Pre-Installed Windows with UEFI This will make sure you boot from your Linux partition AND remove windows 7 from the boot list