Keyboard layout problem with different languages
 

I have added one more keyboard layout to the existing one,
for the Greek language.
One first problem I faced was that no keyboard shortcut was working when I was changing to the Greek language layout. I suppose this is due the different character mapping.
After lots of brainstorming I found a solution.
If I add the same shortcut while I am to the greek layout as a secondary one, then shortcut works.
Obviously this is not a functional solution because I have to do this for every shortcut I need.
What's more, even I spent a day doing so, I'll still face problems because there are also shortcuts of third programs, like Firefox where I am not able (?) to apply the solution I thought of.
Any other ideas of doing so?

I would like to know about this too. I have to toggle back and forth between a Spanish keyboard and English. I made 2 different keyboard layouts, then in Gnome Keyboard Preferences I made a shortcut (Alt + Shift) to toggle between them, but when I use the shortcut, the Spanish layout does not work correctly. It types as it should but the accents do not show up. I have dead keys enabled (which is what I want) and also I found that it works if I go to System Settings and change what type of keyboard I have. Weird.

Maybe for your Greek keyboard try doing what I did which was (in Gnome) go to Desktop -> Keyboard -> Layout Options tab -> Group Shift/Lock behavior. This is what I did and it would switch but it still wouldn't work like it should.