How can I pronounce the "A"? I am confused: when I use it as the article "the" should it be pronounced like in english a (car) or o?
Short a (no accent) sounds a bit like British English "short o" as in "hot". It's a sound that doesn't exist in many American accents.
Long á (with accent) is somewhere between English "short a" as in "hat", and "ah" as in "palm, father, car".
Pretty much regardless of which word those two sounds are in.