"La fille lit un bon journal."
Journal being a masculine noun, you have to use the masculine article "un" and the masculine adjective "bon".
A feminine equivalent would be : la fille lit une bonne lettre
Yes, there is one, you have to learn the conjugation of verb "lire" :
je lis, tu lis, il/elle/on lit, nous lisons, vous lisez, ils/elles lisent.
If you are given the French sentence first, you have two possible translations: "reads" or "is reading".
If you are given "reads" -> lit
If you are given "is reading" -> la fille est en train de lire un bon journal, where "en train de + INFINITIVE" best translates the English continuous form "be VERB-ing"