Can I place my ad banner in the bottom of my screen to be fixed even when scrolled alongside the Bottom navigation

I am developing a B2C application for local business. I will be developing separate apps for businesses and customers but to cater to the customers who do not have the app yet, I wish to provide Businesses with the functionality that they can send invoices to their customer's WhatsApp through my Business App from their WhatsApp Number.

How can I achieve this?

Thanks in advance

i started working on existing react native projet, that have Google ads which is already working on the playStore.

However,is not working on dev environment, is this is normal ? Does the Google ads works only after uploading the app on the store ?