Tonterías translates to "foolishness" or "nonsense." It's a common word, but its use here is particularly evocative.
In the song, Paula Arenas sings, "Estoy harta del tiempo y de sus tonterías" (I'm tired of time and its foolishness). She personifies time, attributing human-like "foolishness" to its relentless passage and the way it complicates things, making it a memorable and relatable expression of frustration.
Paula Arenas opens this one fed up: "estoy harta del tiempo y de sus tonterías" [I'm sick of time and its nonsense]. "Estar harta" is the everyday way to say you have had enough, and it sets the mood for a song about long nights, "miradas vacías" [empty looks] and waiting for someone who has not shown up. Even hope gets a voice here: "la esperanza me insiste que no la dé por vencida" [hope insists I don't give it up for lost].
Then the chorus flips the frustration into something lighter. "Hay tanto tanto tanto para descubrir" [there is so, so, so much to discover] sits right next to "cuánto más voy a esperar por ti" [how much longer will I wait for you], and the repeated "tanto" and "cuánto" make it sound like she is half sighing, half singing herself back up. Her answer to it all is simple and a little wise: "lo simple es lo que vale la pena" [the simple things are what's worth it], because "las manías complican y nos dejan a ciegas" [our hang-ups complicate things and leave us blind]. "Valer la pena" is a handy phrase to steal: it means "to be worth it".