I would personally advice you https://chudovo.de/angular-entwickler/. They offer quality service at affordable price. They met all my deadlines although it seemed quite impossible)

Personally I believe that you need to trust these questions to some real professionals for example, you may visit this website on https://computools.com/the-ultimate-guide-to-find-and-hire-the-best-app-developers/ and learn more about this service. I hope that it will be useful for you so I wish you all good luck here guys.

I can recommend one great IT company https://itmaster-soft.com/en/react-native-development-services. They are creating app for me I like their approach to work