Can't watch your video as I'm at work, but looking at the GParted screen, I'm going to make my suggestions based off of assumptions. Correct me on anything if I'm wrong.
But if SDA7 is the 100GB you're talking about that you want to get rid of... Then do this:
1. Delete the SDA7 partition (100GB inside the SDA3 extended partition).
2. Move the SDA3 extended partition away from SDA2 (your C: drive I'm assuming) so there is unallocated space between SDA2 and SDA3. Use the Move option to just drag the entire partition over.
3. Expand SDA2 into the Unallocated space, by using the Resize option.
Note: backup ANY data that you want to keep in case something wrong happens while the partition editor is running. Better to be safe than sorry, IMO.