3 sentences

1. 这种行为简直是自欺欺人。

   zhè zhǒng xíng​wéi jiǎn​zhí shì zì qī qī​rén.

   This behavior is simply deceiving oneself and others.

   Source: Dong Chinese Dictionary

2. 作为一个诚实的人，无论遇到什么困难都不应当存心欺谩他人。

   zuò​wéi yī gè chéng​shí de rén, wú​lùn yù​dào shén​me kùn​nan dōu bù yīng​dāng cún​xīn qī mán tā​rén.

   As an honest person, one should not intentionally deceive others, no matter what difficulties are encountered.

   Source: Dong Chinese Dictionary

3. 我们决不能坐视他被他人欺辱。

   wǒ​men jué bù néng zuò​shì tā bèi tā​rén qī rǔ.

   We must not sit by and watch him be bullied by others.

   Source: Dong Chinese Dictionary