This does all the things that proofreading does and more, polishing and tightening the text, as well as ensuring that it adheres to style guidelines. Additionally, I will sample fact-check and edit five of your references to determine if you need reference-specific work. 

Original: Unfortunately; three of the 5 shelter–cats were unable to complete the obstacle course without color-coded signs, although one skilfully evaded the task altogether by ploughing through the cardboard walls.

Edit (for American English): Unfortunately, three of the five shelter cats could not complete the obstacle course without color-coded signs. One cat skillfully evaded the task altogether by plowing through the cardboard walls.