Is there a doc where I can learn how to listen to nft events?

Here is the docs from alchemy to listen to events for nft contract - https://docs.alchemy.com/docs/how-to-listen-to-nft-mints

Also, there are indexers which support polygon to index the data. Ex- The Graph, Covalent

Here is polygon docs for indexing the data - https://wiki.polygon.technology/docs/category/indexing-and-querying