this is of course a very widely formulated question. But I can give you some pointer to get you started.
For analyzing text we offer the text mining extension. You can find examples of how these nodes are used on our example server. Another good starting point is as always our Online Self Training https://www.knime.org/knime-online-self-training
As your questions mostly refer to aggregations the GroupBy node is for sure your friend. It offers tons of different aggregations, for various data types.