I don't know either
Yo tampoco sé si te gusto mucho.
I don't know if you like me that much either.
— Running on Empty (1988)
I don't know why either.
I don't know what it's called either.
— Ирония судьбы, или С легким паром! (1976)
I don't know what to do either.
I don't know either.
Yo tampoco sé qué significan, pero informaré a la policía.
I don't know what they mean either, but I'll inform the police.
— Suspiria: Alarido (1977)
I don't really know either.