I am using the user id feature in analyitcs and I am also getting the tracking of user activities. Bt I am unable to find any option to export the report for individual user id. Is there any way to export the report or get the data by GAPI
No, it is not possible.
After processing, session data for which userId was set is available for User ID-enabled views (profiles) in Cross-Device reports. Although the session data is available via the Core Reporting API, the userId field is not available as a dimension in reports and can not be exported from Analytics.
Please refer to this article for further details.
If you would like to retrieve and export data from one specific user, you can do so using Google's User Activity Reporting API. You can see how to do so here: https://developers.google.com/analytics/devguides/reporting/core/v4/user-reporting . If you would like to retrieve your user IDs from Google's Core Reporting API, you can do so by using a custom dimension that has its value set to your user IDs. You would then include "name":"ga:dimension4" (4 is the custom dimension index, just an example) within the dimensions section of the request body for that API.