Probablamente es muy deficil apprender una lungu nueva usando una otra lingua que no hablas FLUENTLY I can empathize!!! (Scusi- ma non parlo bene ESPANOL :)
I think it's worse when you're taking the test in your second language, get it wrong, and realize that it's similar to your native language. Happens a lot to bilinguals that focus on one of the two languages at a given time. x_x;
no, when there is a vowel at the beginning of the next word, you add the "d", otherwise it's hard to string together in speech. Many languages do this, including English ("a boy" but "an apple").