A nod is a yes, a shake is a no, as it is in English - if I understand correctly what you mean by 'shake'.
In my experience, "no" is also often a quick "reverse nod" - the head moves backwards/upwards. Often accompanied by a click of the tongue.
A lazier version of this just moves the eyebrows up rather than the entire head.
Ah yes, how could I forget the "yes" gesture?
(Accompanied, if you say anything, with αμέ in my experience.)
Ευχαριστω is something like this>> ev ha ris TO. Four sylallables. But to understand better try this link which has Greek expressions spoken by native speakers.
I'm sure that repeating the skill you will be given a listening exercise and there is the option to listen to it on regular and slow speed.
Here is a more complete link for the Greek course.