3 sentences

1. 他年纪大了，走起路来很费劲。

   tā nián​jì dà le, zǒu qǐ lù lái hěn fèi​jìn.

   He is old and finds it very strenuous to walk.

   Source: Dong Chinese Dictionary

2. 这几天我总觉得眼睛发蒙，看书有些费劲。

   zhè jǐ tiān wǒ zǒng jué​de yǎn​jing fā méng, kàn shū yǒu​xiē fèi​jìn.

   My vision has felt a bit blurry these past few days, making it difficult to read.

   Source: Dong Chinese Dictionary

3. 这把菜刀非常锋利，切肉一点儿也不费劲。

   zhè bǎ cài​dāo fēi​cháng fēng​lì, qiē ròu yī​diǎn r yě bù fèi​jìn.

   This kitchen knife is very sharp; it cuts meat effortlessly.

   Source: Dong Chinese Dictionary