د has no specific translation or meaning but it is similar to "-ing" in English and not all iraqs use it is the mark of Baghdadi people (original people) . In more popular speach in Iraqi it isn't used like ما اكدر اسمع شي (the ك sound like "g"in "go" ) I can't hear anything ما اكدر اروح باجر للمدرسة (I can't go to the school tomorrow ) ( ك sound like g in go ) (and ج sound like ch in chair with kasrah-i sound)

دَ is used only at the present time and continuous and it has no synonym in Fusha because it is a slang word. دَ اقرا I am reading .

Iraqi as for what i know they use da in replace to want u can use Da or Areed in future and present ما د روح وياكم باجر، ما اريد اروح وياكم باجر اريد اروح هالساعة، د احجي وياكم هسه but for the past ما ردت اروح وياهم

I can't go tomorrow : لا أستطيع الذهاب غدا I can't go right now : لا أستطيع الذهاب الآن

I can't hear is لا أسمع in Arabic I can't is لا استطيع