Mit jelent az, hogy "I'm on to you. "? Fordításhoz kell és nem igazán értem.

Legközelebb így keresd a google-ban: "to be on to somebody":

To understand someone and their hidden motivations.

Child in kitchen being suspiciously quiet, mother looks in suspecting mischief and finding child with suspicious 'butter wouldn't melt' expression: 'I'm on to you. What have you been doing?!'

1. to know about what sb has done wrong

2. to be talking to sb, usually in order to ask or tell them sth