'I don't know yet.' implies doubt about something or someone, eg Are you going to the party? I don't know yet, I might have to work.

the Chinese equivalent of "i dont know yet" would be "我還不知道“ or “我還沒決定” depending on the context.... hope that helps!

the adverb 'yet' would mean: "up until this time / moment" student A: "Are you going to the university this summer?" student B: "I don't know." "I don't know yet." "I don't know" is a straight-forward statement. "I don't know yet" kinda suggests that 'up until this time' student B hasn't decided wether he/she will come to the university in the coming summer class. here, the adverb 'yet' would describe the speaker being uncertain about his/her decision. :)