I have a working apk. I do not know what needs to be done to get testers, trademark a name, advice on pricing, advertising. All the things you want for a good launch to market.
It sounds like you need a marketing agency, not a developer.
I don't see how a marketing agency can help me deploy a app. Marketing comes right after that.
The agency will advise you on go-to-market strategies. They might have staff that knows the steps you need to put it on the store. You also need a lawyer to do the trademark part and ensure all IP you created is adequately protected - you want all moats you get create around you. The very first step might be to find an angel investor that can fund those steps. Have you considered giving Ycombinator a go?