2 sentences

1. 我跟不上你的逻辑。

   wǒ gēn bu shang nǐ de luó​ji.

   I cannot follow your logic.

   Source: Tatoeba

2. 我几乎跟不上他，像往常一样。

   wǒ jī​hū gēn bu shang tā, xiàng wǎng​cháng yī​yàng.

   I could hardly keep up with him, as usual.

   Source: CCMatrix