One professor even went through my entire procedure, painstakingly, I'm not really sure where he got all this time, and he went through and said why each and every step was like the worst mistake I could ever make.
Uno profesor revisó todo el procedimiento, cuidadosamente —no sé de dónde sacó tanto tiempo— revisó todo y minuciosamente en cada paso dijo por qué cada cosa era lo peor que pude hacer.