Question

Give the important themes,performances,highlights or important events that happened during the art period of greek theater

Answer 1

If you want to know where you can go to read about the themes you mention, there are two places you can go. First, there are the primary sources - the plays themselves. We have three main tragic authors - Aeschylus, Sophocles, and Euripides. If you read a few plays from each author, then you will get a good sense of what Athenian tragedy is like.
Second, you have secondary sources. There are several excellent books on Greek tragedy. These books with help you with what scholars are saying about the plays.
I suggest that you start with basic introductions. A good book is: Ancient Greek Literature by Kenneth Dover and E. L. Bowie. This book will give you a good overview of tragedy. Another good book is Ancient Greek Tragedy by H. D. F. Kitto. Also use the bibliography to read books and article that interest you.
Finally, you might want to get a basic history of ancient Greece, so that you will know what is going on during the time of these tragedies.