Hi Federico, By "make some English certificate", I'm guessing you mean to ask whether you should take a standardized English exam, like IELTS. I can only speak for companies in my area (Toronto), but I've never heard on an employer requiring proof of an English proficiency exam like that. Once someone at the company is speaking with you or exchanging emails, they can assess your proficiency very quickly and tell if it's sufficient for the position. Good luck!

English certificate...? What is that?