Hey I'm a Senior Android Developer, your Job description hocked my Attention really fast, the idea of upgrading an existing application with Firebase, Layout Adjustments and MySQL db management is great. So if you are interested in working with an expert, avoid problems and receive a great service then jump lets jump on free initial call(10min) and talk about the details, so I will be able to help you, in very effective way.
Best Regards,
Semen Vyshnyevetsky