弄明白

我没弄明白这个笑话。

wǒ méi nòng míng bai zhè ge xiào hua。

I don't get the joke.

假如你在老师讲课的时候再集中一点去听讲的话，你应该就能弄明白了。

jiǎ rú nǐ zài lǎo shī jiǎng kè de shí hou zài jí zhōng yī diǎn qù tīng jiǎng de huà， nǐ yīng gāi jiù néng nòng míng bai le。

If you'd listen a little more carefully to what the teacher says, you'd probably be able to understand.