I have to upload a new application, It\'s just the design that\'s a little different. Yesterday I generated the keystore file to sign application. Can I use the same?
The official documentation tells us:
In general, the recommended strategy for all developers is to sign all of your applications with the same certificate, throughout the expected lifespan of your applications. There are several reasons why you should do so ...
https://developer.android.com/studio/publish/app-signing.html#considerations
So yes, try to sign all of your applications with the same certificate.