lg g3 android-6-0 help

Hi Guys,
I hope someone will help me.

I was following this on my lg g3 16gb (uk) http://ift.tt/26I3Tfr
and my cable came off and it got stuck I tried to go into download mode again and it wont let me. It goes for 1 sec and there is some error message on top that stays for 1 sec too. "boot verification failed: cause MISMATCH_SIG_LEN
I tried safe more etc nothing is working. And phone keeps loading lg logo.

I dont really understand rooting etc. I tried almost everything that I found but nothing is working. Can anyone help me? :(

Thanks

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