Chinese learners move from characters to idioms as the highest level. This free resource explains 「臨陣磨刀」 below.
For this session, we will be discussing the idiom 「臨陣磨刀」. See below for its meaning and practical usage.
Lin: arrive, about to; Zhen: go into battle. Only sharpen your swords and guns when you are about to go into battle.
The Mandarin pronunciation of this idiom is :
lín zhèn mó dāo
while its Cantonese pinyin is :
lam4 jan6 mo4 dou1
The collection of Chinese idioms is enormous, with each one holding its own meaning and purpose. We hope these resources can assist you in better understanding and learning Chinese.

