当时街上人太多了，我也不知道是谁偷我的手机。

Dāngshí jiēshàng rén tài duō le, wǒ yě bù zhīdào shì shéi tōu wǒde shǒujī.

At that time the street was too crowded, I didn't know who stole my phone.

我还记得我们的第一次约会，当时我们是坐在窗边的位置。

Wǒ hái jìde wǒmen de dìyī cì yuēhuì, dāngshí wǒmen shì zuò zài chuāngbiān de wèizhì.

I still remember our first date, at that time we sat next to the window.

我当时不知道他已经回家了。

Wǒ dāngshí bù zhīdào tā yǐjīng huíjiā le.

At that time, I didn't know he had already gone home.