Voice/Alarm Notification

I am a student and I have 3 to 4 classes in my chool every single day, but I cannot remember the class time and sometimes I miss my classes. I just want to set a voice reminder for a particular class, so that 5 minute before my class starts, I get a buzz/ring/sound notification to be alerted/get ready for the class.

Since I am not earning, so I am looking for a free app, where I can be on time for my classes. kindly help me with the step by step direction, how to set up voice reminder alert, so that I can get ready few minutes before the class.

Thanks,

AJ