Yes, that is a problem with this sentence. Try to get beyond the ABC skill and go on to other levels which don't have this problem.
Here are some links to help you:
THE GREEK ALPHABET
What the letters look like, how they sound, how to access your Greek keyboard, how to find the letters on the keyboard, how to add accents. There are many resources, podcasts etc
Here is the Greek Forum for further information:
If you have questions just ask.
The fastest way to change from one keyboard to another on a PC (or Mac) is by using keyboard shortcuts. On a PC, it's usually Alt+Shift or something similar and in any case you can set a combination that works best for you in the settings. Don't waste time by selecting keyboards with a mouse. For mobile devices all it takes is pressing a globe key or similar - it all depends on the specific device.
The sequence of the questions is set automatically by the system, so single-language answers cannot be grouped together. Don't worry though, it doesn't take much time to get used to using more than one keyboards! It does mean that you will find yourself typing with the wrong keyboard every other sentence, it happens to all of us all the time, you just erase, switch and start typing again! :) (I'm still not sure whether having different keyboards between different programs makes things worse, but I always set my computer to allow it...)