somehow, but
Aún no sé cómo, pero lo conseguiré.
I don't know how yet, but I'll achieve it.
— Comer, beber, amar (1994)
I don't know how, but he did it.
No sé cómo, pero de repente se ha hecho más hermosa.
I don't know how, but she's suddenly become more beautiful.
— Nausicaä del valle del viento (1984)
I don't know how, but I know.