successful deployment but.failed when connecting to the database
Hey @hanifa, welcome 
A couple of things come to mind:
Does the application run fine locally, running yarn rw dev?
If so, then please read Deployment | RedwoodJS Docs through from top to the bottom to make sure everything is setup correctly. This includes setting the necessary env. vars and db connections.
If everything is good there, it is probably worth digging into the error logs to see if you can find out what is happening.
Please let us know if you need more support.
Regards,
Barrett