I see that you've been learning Spanish as well. I bet you can see the similarity in accent in some cases. If an English speaker managed to get over the pronunciation differences between their native language and Greek, they could pronounce almost any greek word correctly an drealize how well everything flows when they speak. ^.^
haha, I actually learned Spanish in school and then from natives, I finished the tree in a day or two so that I could tell other people what all they can learn from Duo! :P I still need the stress marks in Greek because it seems like half of the words have the accent in the beginning of the word and the other half has the accent at the end. In Spanish most words have accents on the penultimate syllable which is very natural, the only words I can think of off the top of my head that have accents on the end are the preterite conjugations like "Hablé con la chica ayer" or "Les gustó escuchar su idioma de la boca de un extranjero".