4 sentences

1. 他跑得太快了，我很难跟上。

   tā pǎo de tài kuài le, wǒ hěn nán gēn​shàng.

   He runs too fast; it's hard for me to keep up.

   Source: Dong Chinese Dictionary

2. 我们要跟上时代发展的步子。

   wǒ​men yào gēn​shàng shí​dài fā​zhǎn de bù​zi.

   We must keep pace with the developments of the times.

   Source: Dong Chinese Dictionary

3. 我们的教育必须跟上时代的发展。

   wǒ​men de jiào​yù bì​xū gēn​shàng shí​dài de fā​zhǎn.

   Our education must keep pace with the times.

   Source: Dong Chinese Dictionary

4. 他的思维非常跳跃，别人很难跟上他的逻辑。

   tā de sī​wéi fēi​cháng tiào​yuè, bié​ren hěn nán gēn​shàng tā de luó​ji.

   His thinking is very jumpy, making it hard for others to follow his logic.

   Source: Dong Chinese Dictionary