Power the phone down completely, and then try entering download mode. The error message you get with the red triangle is normal.I don't know what I missed, but now I get Your device is corrupt. It cannot be trusted and will not boot. I'mma try to flash back my system and try it again.
H860 with Nougat and anti-rollback version 0
P.S : I can't enter recovery or download mode ... how much I'm I screwed ? It just keeps rebooting