complete pwa with push notifications

Hi, I need I pwa for an existing wordpress website, it has to have splash screen, seo optimization, push notifications (like any app sotre app, so i need an admin area for the push notifications), off line access, it has to be compatible with the major operating systems (android, iphone etc..). I need continous support if needed so I will prefer a webagency that can offer quick support for future development or fixes. I need a preliminary phonecall with the developer in order to clarify the variuos aspect of the job. Thank you