Hyundai Eon ERA 2011 model- Mileage and gear vibration problem?

last year me and my family decided that we will buy a small car and in weekends we will go for holidays,picnic and all to make our weekends more joyful. and after a lot of research i came to finalise hyundai eon era and i bought it. The car was really good but not enough power ful to drive on highways or stuff like that.

When i took it from kanpur to lucknow last weekend it started giving mileage as well as gear vibration problem. Please help what should i do to fix it.