My iPhone 6s Plus bring out Estimating time remaining what should I do next ?

You will need to connect to a Wifi network. A hotspot connection will not work to complete the update

You will need to charge the battery and leave it attached to the charge circuit.

After doing those steps, attempt the update again.

Yeah...I’m using my second iPhone 6s to on hotspot for it

As stated: a hotspot connection will not work to complete the update.