expression
a little learning is a dangerous thing
Proverb warning that superficial knowledge can lead to serious mistakes or harm.
生兵法は大怪我のもとだから、きちんと勉強してから挑戦したほうがいい。
A little learning is a dangerous thing, so you should study properly before trying.
A traditional Japanese proverb. The exact origin is uncertain, but it reflects a common caution against half-baked knowledge.