So far as i know you can also flash after the rom baseband but there would be some issues then, modem is like your modem in your home it receives data and also sends it for sensors,wifi,cellular etc.
Kk baseband download link: download the d802 one https://www.androidfilehost.com/?w=files&flid=12880
Doesn't matter that you are a noob, after a long time in android and forums here you will not be an noob anymore but an experienced user
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