I've been on and off Duo for years. Currently doing Norwegian. I have done the Spanish tree three times twice from French, once from English. Also German from French. It's a good system for learning syntax and grammar and vocabulary. Worthless for conversation. How well you can train your ear depends on the language. Spanish, for instance, is based on the Columbian dialect with the soft 'g' sound for 'y'.
Different pronunciation / accent doesn't ,mean "dialect".