install GAPPS (play store,google account) in an unrooted android phone

Hello i have the Nubia NX535J android phone (its the Nubia Z11 Max with 3 GB ram) it is unrooted and has a chinese rom installed (i wrongly downloaded and overwrited the english one that was installed) this chinese rom doesn't have the google apps installed i didn't find any custom rom or recovery (twrp etc) to use on the internet -- with checked OEM unlock, usb debugging, "allow mock station" enabled and booted in bootloader i tried to type from a windows machine and command prompt "fastboot oem unlock" "fastboot flashing unlock" but the phone replied "unknown command" --- if you had any idea how to install the google play store together with the google account (to use gmail,google calendar etc) in this phone would be appreciated please bid only if you accept till 35,00 euros