You are facing an under 21 DUI case because your chemical test came back at .05% under Vehicle Code 23140. You are subject to fines and losing your driving privileges for up to one year. If convicted of this charge, it will also be counted as a prior offense for the next 10 years. Do not discuss the facts of your case and make admissions on an open forum like this. Go see a criminal defense attorney for a free consultation to discuss your case, including errors on breath machines, etc. Good luck.
You need to request a DMV hearing within 10 days from the date of your arrest or the DMV will suspend your driver's license for a year. Because you're under 21, you're facing a "zero tolerance" situation because you shouldn't have been drinking at all. That being said, there could still be defenses in your case, for which it would behoove you to speak with a DUI defense attorney in your area to discuss.
Based on the facts as you have stated them you will only be looking at an infraction and not a full DUI, which is the good news. The bad news is that you may lose your license if you do not successfully win your DMV hearing. I would recommend hiring an attorney to represent you to preserve your CDL.