After trying to install magisk trough twrb i can oly go in downloadmode

hi, (mobile: samsung galaxy s6 sm-g920f)

So i wanted to play the new pokemongo update and start looking for solutions.
i found that you can play pokemon trough magisk.
before you could install magisk you have to download twrb.
so i did that and i was in the menu of twrb and i did a factory swipe and after that i tryed to install magisk.
after that the phone was constantly rebooting and i tryed to get it fixed again.
and i went trough many steps and now i am stuck with a phone that doesnt want to reboot.
The only thing i can do now is download.

( i tryed to install roms for it to work and i am now waiting on the original firmware of my phone so i can flash it on my device and hopefully solf my problem.)

Does someone know how to fix this Thanks in advance

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