Most newbies pedal too slowly. Your legs work most efficiently around the rate of a brisk walk, ie about 70 revs/min.
You should pedal against some resistance, but not too much. Use your gears to set resistance and keep resistance as constant as you can by shifting as the terrain changes. Again, you should be breathing at the rate of brisk walking.
If you pedal too hard, you work too hard and it is more like running.
Cycling athletes prefer to work at running rate but there is no rule that you have to ride at max speed.
You should pedal against some resistance, but not too much. Use your gears to set resistance and keep resistance as constant as you can by shifting as the terrain changes. Again, you should be breathing at the rate of brisk walking.
If you pedal too hard, you work too hard and it is more like running.
Cycling athletes prefer to work at running rate but there is no rule that you have to ride at max speed.