Keep pressing power +volume down buttons until boot loader appears.
select wipe data/factory reset and execute
Then simply apply the rom from the area you downloaded it(sd card-sdcard2.....).
If that fails simply download the official stable english, store it in the phone sdcard and then apply.
Before apply make a factory reset/wipe data again.....
(you are loosing any apps and data so better make a back up from icloud of the phone so you can later restore it, in the case you have stuff you want in the phone)