Okay kiddo, let me explain what sackings of Goa and Bombay-Bassein were.
Do you know what a war is? It's when two groups of people fight against each other. Back in the olden days, the Portuguese had control over a few places in India like Goa and Bombay-Bassein. They used to do very bad things to the people living there, like taking away their things or forcing them to work.
The Indian people didn't like this, so they decided to fight against the Portuguese to get their freedom. The Indian soldiers fought very bravely and they defeated the Portuguese soldiers.
After they won the war, they went into the Portuguese cities of Goa and Bombay-Bassein and took away all the things that the Portuguese had. This is called a sacking or looting. They did this because the Portuguese had been very mean to the Indian people and they wanted to show them that they were not going to tolerate it anymore.
Even though the sackings were not good, it was a way for the Indian people to show that they were strong and wanted to be treated fairly. Today, Goa and Bombay-Bassein are a part of India and the people living there have their freedom.