The Ancheer looks like it has a newer type battery with the controller inside it, plus the usual hub motor. The non-ebike parts can be easily replaced.
If the motor burns out, you can get another one geared motor for under $200, with wheel. Some will even have a cable that matches.
If the electronics fail, you can buy a better controller with LCD display for $60 except it won't fit inside the controller and you'll have to splice in the brakes, throttle, and pedal sensor.
If the battery dies, post its details and someone can probably direct you to where you can buy it.
If you only paid $400 for the bike (it's $650 new) , you have to decide how much more to spend.