Same tune as the French monk who overslept - but in China the round belongs to two tigers, one with no ears and one with no tail, and the song's verdict is the same one you will reach: 真奇怪 (zhēn qíguài), really strange.
The grammar earning its keep here is 得 (de) in 跑得快 (pǎo de kuài) - runs fast. That little 得 is how Mandarin bolts a "how well" onto any verb, and this song installs the pattern permanently. The other quiet lesson is the measure word: tigers come in 只 (zhī), so it is 两只老虎 (liǎng zhī lǎohǔ), never 两个老虎.
One warning that applies to every Mandarin song: melody replaces tone. Sung Chinese cannot show you that 虎 is a dipping third tone, so use the song for rhythm and vocabulary, and let the word pages and their audio put the tones back. The word 老虎 (lǎohǔ) itself sits far beyond this chapter's word list, which is exactly why a song carries it better than a drill would - some words you simply keep.