Why are these changes needed?

clean up codes & update community talks

Related issue number

Checks

• I've included any doc changes needed for https://ag2ai.github.io/autogen/. See https://ag2ai.github.io/ag2/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.