I'm Dutch, so don't worry you'll get a real pronunciation from me :)
"aa" is indeed "ah:"
"d" at the end of a word is a "t"
Good to know you're French, no I can give you a better example then in English:
Tjaard's beginning TJ sound is like the beginning sound of
Thierry.
(so that would make the the French phonetic version of
Tjaard: Thiart (with the a said a tad bit longer than in French))