The character for "they" is used singularly or plural. Based on auditory context you can ascertain if "they" is meant to be a singular he, she, or they. When written, 他 (ta) and 她（ta) are pronounced the same. Note the female stem on the left of 她
Stems (left, over, or under) position-wise can aid you in identifying characters. Base characters (typically to the right, or largest set of strokes) can aid you in identifying what the character sounds like. I am not a linguist and do not have linguistic background so apologies if this is wrong. Generally this is how I try to identify mandarin characters.
Another fun thing is that there is no conjugation of verbs. You describe the tense of the verb by adding modifiers after or before.
| Eat | 吃 |
| Eating | 在吃 |
| Eaten | 吃了 |
| Ate | 吃了 |
| Will eat | 会吃 |