Hello @ShirleyC11
Thanks for reaching out to the Instructure Community. If you have a group assignment and the groups have submitted but you want to re-assign the assignment to specific students who need to re-submit or didn't contribute etc. you can do so. If this is what you mean by "Return the file" then you'd need to make sure the assignment is open for multiple submissions. Additionally, you may want to go to the assignment settings and enable the option for individual grades:
How do I grade group assignments in SpeedGrader? - Instructure Community
The single students can then re-submit the assignments and you can give them individual grades. Keep in mind that other students would likely be able to see another submission if you don't have the assignment hidden. Also, any comments left in the speedgrader would be available to all students in the group assignment but you can leave individual comments for specific students by clicking on the cell for their grade within the gradebook. Hopefully this helps!