Not able to use same query in oracle

Question

I am new in oracle so I am not able to write this query in Oracle its showing me some compile time error
main issues are:
1) Not able to use @@identity option which is in sql and return last inserted id (as its auto insert value)




ALTER PROCEDURE [dbo].[Insert_Update_Students](
,@SelectedCourse varchar(4000) = NULL
,@StudentID int = NULL
 output
,@UserID int = NULL
,@YogaBefore bit = NULL
,@YourComment varchar(250) = NULL
)
AS  BEGIN
SET NOCOUNT ON;
IF(@StudentID IS NULL OR @StudentID <= 0)
BEGIN
INSERT INTO Students( [AboutUs]
,[SelectedCourse]
,[UserID]
,[YogaBefore]
,[YourComment]
)
VALUES(
,@SelectedCourse
,@UserID
,@YogaBefore
,@YourComment
)
set @StudentID=@@identity;
END
ELSE
BEGIN
UPDATE Students SET  [AboutUs]=@AboutUs
,[SelectedCourse]=@SelectedCourse
,[UserID]=@UserID
,[YogaBefore]=@YogaBefore
,[YourComment]=@YourComment
 where
 [StudentID]=@StudentID

END
END