How to get my phone back to stock and working?

[AC Question]

Ok so i was flashing roms on my htc one m8 and its not booting into the rom. It just stays at the google start screen and then goes back into recovery (twrp). Im trying to flash more roms but its not working, just the google sign. My phone is s-off and im tring to flash zip RUU but i just get errors. Plz help, im pretty noob about this stuff.