Anna: There's a flashing light on my air-conditioner. José: A cleaning needs to be done on the air conditioner each 6 months. You need to replace "each" with "every". "A cleaning needs to be done on the air conditioner every 6 months." More natural to say, "The air conditioner needs to be cleaned every 6 months" Anna: Who will do a cleaning on my air conditioner? "Who will do the cleaning of my air conditioner" Or "Who will clean my air conditioner". José: My main staff will clean the air conditioner. "My main employee will clean the air conditioner" More natural to say, "My most experienced employee (or "my head employee") will clean the air conditioner" Anna: Now? José: He will start to clean your air conditioner in an hour. Anna: Ok. I will wait. Jose writes down a small paper: 'Carlos needs to start cleaning the Ana's air conditioner at 4 pm' 'the' before 'Ana' needs to be removed. "Carlos needs to start cleaning Ana's air conditioner at 4 pm"

I think Antalki's "notebook" feature is better for this question, but let me try anyways: Anna: There's a flashing light on my air-conditioner. José: Cleaning needs to be done on the air conditioner each 6 months. Anna: Who will clean my air conditioner? José: My head of staff will clean the air conditioner. Anna: Now? José: He will start to clean your air conditioner in an hour. Anna: Ok. I will wait. Jose writes down a small paper: 'Carlos needs to start cleaning Ana's air conditioner at 4 pm'