Question

one feels difficulty to breadth in deep well while cleaning

Answer 1

a deep well is A well that gets its water from under shallow impermeable levels, deeper than 22 feet.
I believe modern technology has also allowed cleaning deep wells faster by just using chemicals such as chlorine. If probably cleaning deep wells require a man to go in, the most probable reason that he will have a hard time breathing is due to the presence of low oxygen/air inside the well. first there would be no ventilation, as he goes deeper oxygen levels inside the well will just deplete. Since no circulation of air is present breathing in the adequate amount of oxygen for biological respiration would be hard....

like putting one hole in a closed can and pouring out the fluid...the result would be the fluid pouring out with difficulty. But if we put another hole, air can circulate inside thus making it easier to pour the content....

since deep well only have one hole/opening air will be having a hard to circulate inside/out...

Hope this helps. This is how I see why it would be hard to breathe while in a deep well. :))