Hey,
I can easily built you an car washing mobile app for your business in android and ios.
Since I have a lot of experience in designing and developing mobile applications and have worked on several projects before similar to your requirements, I am quite confident to get this done as per your requirements and need.
You can check my portfolio from here https://www.freelancer.com/u/TheCodeSolutions
I will be waiting for the prompt response from your side, thanks.