Unfortunately, the battery life is not sufficient for this. Most smartwatches from phone manufacturers are simply miles behind. If displaying calls and messages are really the only important things for you, I think you'd be better off with a Garmin watch: e.g. the Garmin Venu 2. It displays calls and WhatsApp messages and, if you want, all the notifications that you also receive on your phone. The battery lasts 6 days for me. I run about 5 km (45 min) every day.