This is a very complicated subject and many learners get a lot of headache. Why is girl neuter, this does not seem to make any sense, it should be female, shouldn't it? But there is a rule: All nouns ending with a 'chen', are neuter. There is a complicated sounding word like diminuitive.   A diminutive is a word that has been modified to convey a slighter degree of its root meaning, to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment. An example: der Tisch (table) is masculinum, but das Tischchen (a small table) is neuter.

Bascially you have to learn with every noun its article as well, but thank God there are some rules:

<a href="https://deutsch.lingolia.com/en/grammar/nouns-and-articles/gender">https://deutsch.lingolia.com/en/grammar/nouns-and-articles/gender</a> ;(in English)

<a href="http://www.passion4teq.com/articles/der-die-das-genus-regeln/">http://www.passion4teq.com/articles/der-die-das-genus-regeln/</a> ;(in German)