Using your Merida Big Seven 10D mountain bike is easy. Just adjust the seat height to your comfort, hop on, and start pedaling. When shifting gears, use the Shimano Tourney 3x7 speed drivetrain. Push the lever gently to change gears smoothly. For braking, squeeze the hydraulic disc brake levers. This will give you reliable stopping power in any situation. When riding on trails, be careful of bumps and obstacles. Try to maintain a steady speed and balance. For maintenance, regularly check the tire pressure. Keep the tires inflated to the recommended level for a smooth ride. Clean the bike after each use, especially if you've ridden in muddy conditions. Use a mild soap and water to clean the frame, wheels, and components. Lubricate the chain every few rides to ensure smooth shifting. Check the brakes regularly for wear and tear. If the brake pads are worn out, replace them promptly. Also, make sure all the bolts on the bike are tightened properly to avoid any loose parts during your ride.