That is, always supposin' your supposin' is right." 
That is, always assuming your assumptions are right.
That is, always doubting what you suppose.
A human digging
The dirt-bike racer is on the bottom of the pool making turns.
People gathered outdoors for a sports match
A cyclist pedaling away from the crowd.
It was shown that real change is not easy.
2 girls are sitting next to another girl wearing a costume