First fetch all changes of main branch (i.e updated branch). Second go to branch (i.e branch has conflict) fetch branch changes. Then open git hub terminal and fire following command

1. git merge “updated-branch-name” and click on enter.
2. git diff —name-only —diff-filter=U this command show files that has conflict, then resolved conflict of files and enter last command.
   3.git commit -m ‘Commit message’ enter this command to commit your changes after conflict resolved.