Hello Kulwant,
Thank you for posting your question in Bentley Forum.
For exporting a design plan to .dwg, please refer the below link for your reference.
communities.bentley.com/.../130380
And about exporting a Section to .dwg, I would suggest you, please give extension .dpw for cross sections under working drawings option and then move further to export to dwg.
Regards,
Purva Lakde