Problems while updating the actual work hours

When I update the actual hours for completed task, the actual finish date does not get updated. when I manually type in the actual finish date, the % complete changes to 100%, duration gets automatically calculated(which is totally wrong), actual hours changes and it is equal to work and rem work is 0hrs.

Note: Effort Driven is unchecked.

When I have Effort Driven checked, I dont face the above problem but when I enter the actual hours, it modifies the actual start and actual finish dates.

How do I handle this problem??? Any help is appreciated.

Thanks