、。
I need to find the cause quickly, fix my slump, and live up to Senior Tanizaki's expectations.
Literal
Quickly cause [object-を] find, slump [object-を] cure-and Tanizaki-chief [genitive-の] expectations [to-に] respond-must.
A determined inner monologue. ~ないと (at the end, the implicit ~ないといけない or ~ないとダメ) is a casual obligation frame, meaning 'have to do X,' 'must do X' — the truncation is common in spoken language where the listener completes the thought. 期待にこたえる is a set expression: 期待 ('expectation') + に + 応える/こたえる ('respond to, meet, live up to') = 'live up to expectations,' 'meet the hopes [of someone].' 主任 ('chief, senior, principal') is a workplace title below 課長 (section chief) — the kind of senior colleague a character would defer to.