Having trouble when saving.....

I save the project. Then when I want to get back working on it. I'll open it and it will the file will say,  File is actively in use or is read-only. Would you like to open the file read-only?

 

Read-only will not let me save the work I worked on it?

I guess I will restart and save it some where else this is going to put me back. College student and it seem every time I start some thing it doesn't want to get finished. lol

 

What sucks is that this is a grade.