modify an existing app (reverse engineering)

hello. there is one app on the playstore. you input a car plate , you click enter and as a result you get if it has insurance yes/no and if it is stolen I want to modify that app (tried to contact the developer, but no answer after 3 weeks) so that, instead of input manually the car plate, i want that it automatically reads the car plates from a plain txt file , it checks the car plate (using a random delay of 30-90 seconds between each car plate), and then save the results in a new output txt file are you able to do it?