Learn Icelandic: Sérð þú bíl hér?

Bíll is the dictionary form, which is used when the car is the subject of a sentence. In this sentence, the car is the direct object (the thing being seen), so it must take the accusative case. For this word, the accusative form drops the last l, becoming bíl.

Why doesn't the sentence use a word for "do" like the English translation?

Icelandic doesn't use helper verbs like "do" to ask questions. Instead, you just swap the order of the subject and the verb. So, the statement þú sérð (you see) simply flips to become the question sérð þú (do you see).

There is no word for "a" in the Icelandic sentence. How do we know it means "a car"?

Icelandic doesn't have indefinite articles (the words "a" or "an"). A bare noun like bíl just means "car" or "a car", depending on what makes the most sense in English.

What verb does sérð come from?

It comes from the verb sjá (to see). This is a very common but irregular verb, which is why the vowel changes completely from á to é when conjugated for "you" as þú sérð.