High Skilled Xamarin Developer with experience in Win Phone

Hi You need to have Xamarin experience in Win Phone 8.1 and 10. If you have Win Phone Device, that's fine but it's so important. Could you please answer the following question? How to change font size of navigation bar in Win Phone? Our large project has some issues of Rendering UI of Win Phone but all is good on Android and iOS. That's long term project. If you have correct solution or experience in this field, please answer ASAP. Happy bidding.