Learn Turkish: Kız yeni bir resim boyuyor. - The girl is painting a new picture.

The root of the verb is boya- (to paint). When a verb root ends in 'a' or 'e', adding the present continuous suffix causes that vowel to change or narrow. Because the first vowel in the word is 'o', the 'a' narrows to 'u', making it boyuyor.

Why is the word order yeni bir resim and not bir yeni resim?

In Turkish, adjectives usually come before the word bir (a/an). So instead of saying 'a new picture', you literally say 'new a picture' (yeni bir resim).

Why doesn't the word resim have an accusative case ending here?

We only use the accusative case ending for specific, definite direct objects (like 'the picture' or 'that picture'). Because the girl is painting an indefinite object ('a new picture'), resim stays in its plain dictionary form.

Does resim only mean a painted picture?

While it means a painting or drawing here, resim is also the general word used for pictures and photographs in everyday Turkish, even though the exact word for a photograph is fotoğraf.