Netgear Nighthawk M6 MR6110 After factory reset display is in spanish

Since it's in Spanish now, the best way to proceed is to do a factory reset again.  This time you need to use the hardware reset method.  There's a small hole on the bottom of the case near the connector side.

Just insert a device like a paperclip and hold the button down for 10 or so seconds.  The device should perform a reset.

Here's the exact wordage from the manual:

To perform a factory reset using the reset button:
1. Remove battery cover, but leave the battery installed.
2. Locate the reset button.
The reset button is inside of a small hole labelled RESET.
3. Press and hold the reset button with a paper clip or similar object for up to 10
seconds.
Use only gentle pressure. Pressing too hard or using a sharp object will damage
your hotspot and might void your warranty.
4. Release the reset button.
Your mobile hotspot displays resetting…
Your mobile hotspot is reset.

I would advise you to download a copy of the manual to help with future issues.  Here's a link to the manual

Nighthawk M6 Pro, Nighthawk M6 Manual (netgear.com)