True, but I suspect they are sufficiently rare not to constitute an argument for a beginner not to learn English
(also, correct me if I'm wrong but most of those words have accents because they come from other languages)
English had native accents, as in naïve, to show that the double vowel was pronounced as two sounds, but they have declined in use over the year. Cooperate isn't spelt with 'oö', which makes pronouncing it from the spelling difficult. But English has never really been spelt phonetically anyway, so it is now overdue for a reformation really.