I dunno.?? If I were you I would take portions of the ride and really dig in, forcefully bring up the mph by going to the small rings out back and bare down. Dig in. Look up ahead of you and choose a shadow, or a mailbox and set your goal to get there while still putting out energy. Then rest by coasting. Do this once every mile. Your goal can be a short distance in the beginning. But focus on doing this throughout your ride. 6 to 8 miles is a good ride for a beginner. Use those miles to get stronger. There's a price to pay. It's up to you how much you want to spend in sweat to achieve. And pain too. It's a balance. Maybe talk to a nutrition expert along the way.