If "Grammatica Greca" by Vivian Sivieri is a required text for your studies, your best course of action might be to consult with your teacher or the curriculum department. They may have recommendations or resources available that are specifically tailored to your educational needs.
If you are looking for specific grammatical rules or exercises from this manual, you can find physical or official digital copies through retailers like Amazon Italy summary of a particular rule (like the Greek verb system) from this grammar? Sivieri Vivian Grammatica Greca Pdf 11l