Keys are locked in the trunk and the trunk release handle in the driver's is broken. How do I get my trunk open? is there a emergency handle in the trunk?

RTFM

"If your vehicle ever loses power, you can open the trunk by lowering the rear seat and pulling the emergency trunk release handle located inside the trunk. See Split Folding Rear Seat on page 1-10 and “Emergency Trunk Release Handle” following."

no year car told. the now lost free users guide is by year.
made 1994 to present (even 1989 as legacy outback)
no country told at all
sorry cars not the same world wide.

open glove box, read the users guide? oops locked too>?
most cars sold in USA , called wagons
opening the rear gate hatch by accident driving
kids fall the ground, or cargo hits cars behind you. (so is illegall that feature)
and is never called a truck ever, in a wagon
only on sedans. a hatch or 5th door it is named.
In Europe then even call them 5 door cars.
so I am confused.
so all keys lost to the car. and can not drive it
nor open any side doors
and rear hatch is locked and valuables in cargo area to fetch, right?
I say call a locksmith
and pick the lock.
the door lock(mechanism) in the hatch internal, is accessed from the inside of the hatch open.so no why to attack it that way.

call a locksmith,

Here's what you need Trunk Monkey Compilation

As in your button is failing? open back seats and pull emergency internal release, or use key

Open the window and reach out to open the door with the outside door handle,before closing the door and locking it, remember to put the window back up.

As for the trunk it should have a emergency release trunk handle from the inside.

the emergency release for the trunk is on the trunk. the next time you open your trunk, look up at the inside of the trunk lid. you should see a white glow in the dark T-handle hanging from a small cord with instructions wrote on it. this is the only emergency trunk release on the car.

All newer vehicles have an emergency manual trunk release inside the trunk.

This should be basically a rip cord directly attached to the trunk locking mechanism. Most modern ones have a yellow handle on the ceiling of the trunk that will release the trunk latch if it is pulled. Yours may be a different color, but if you get in there with a flash light you can probably trace a steel wire from the trunk latch back to some sort of handle that looks like you can pull it. Its definitely worth a shot.

You should be able to take vin # to BMW dealer and they may be able to help

Emergency operation of rear lid
If the rear lid cannot be opened with the radio
remote control (e.g., if the battery of the remote
control is dead), the emergency operation must
be performed:
1. Unlock and open the driver's door with the
vehicle key.
2. Switch on the ignition so that the alarm system
will not be triggered.
3. Check if the TAILGATE function is activated in
the multi-purpose display of the instrument
panel.
Please observe the chapter “TAILGATE” on
Page 119.
4. Press the central locking button in the armrest.
The rear lid is now unlocked and can be opened
with the unlocking handle

Sounds like the cable for the emergency release handle on the trunk cover is binding. Seen a few where the cable isn't passed in the right spot and the moment is shifts the trunk opens because the cable has too much tension. Also seen broken emergency grab handle just a little broken that will do the same because the cable is not in the right position. Usually a defective latch you will have problems closing it too.