Subject + 认真 + Verb
The adverb 认真 (rènzhēn) means "seriously" or "earnestly" and describes doing something with careful attention and sincerity. When used as an adverb, it is placed before the verb to modify the action. It can also function as an adjective meaning "serious" or "conscientious."
他做事特别认真,从来不马虎。
tā zuòshì tèbié rènzhēn, cónglái bù mǎhu.
He's very conscientious in his work and never careless.
你得认真听老师讲课,别老走神。
nǐ děi rènzhēn tīng lǎoshī jiǎngkè, bié lǎo zǒushén.
You need to listen to the teacher carefully and stop zoning out.
她认真地看了一遍合同才签字。
tā rènzhēn de kàn le yī biàn hétong cái qiānzì.
She carefully read through the contract before signing it.