Battery

iPhone 11 doesn’t ship with a charger.

Which charger do you have, at what wattage?

Here are the common Apple USB chargers: About Apple USB power adapters - Apple Support

Apple has available higher-wattage chargers, and these can work with iPhone 11: Fast charge your iPhone - Apple Support

It’s also possible that the charger you have is somehow faulty.

Not entirely clear to me what sequence is happening here.

Here is what Apple suggests: If your iPhone or iPod touch won't charge - Apple Support

A battery health display below about 80% is headed for battery replacement.

If you’re using a lower-wattage charger (5W, etc) at the same time you are using the iPhone, it won’t charge as fast and might even drain under active use.