blue background images looks better with black phone form. I changed design with client requirements like in overlay background but phone does not looks good much like in first.  How do i make better look of second design. background and phone are not looking better.

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Try changing the color for your phone from black to something lighter.

Developing a mobile phone application is a very difficult and costly task. I know this by myself, because for several years I have been developing applications. As for the logo, I can advise you to turn to professionals who will make the logo as pleasant as possible and that which will open your application from the best side.