It doesn't fully convince me.
'Convince' — con-VIN-ce. Stress on the second syllable. 'Del tutto' = entirely, completely.
Use to express partial scepticism — you're not completely against something but you have reservations. More diplomatic than full rejection.
'Convincere' (to convince) is a key verb for Italian opinions — 'mi convince' (it convinces me) vs 'non mi convince' (it doesn't convince me). 'Del tutto' (entirely) makes it partial — you're partially unconvinced, not totally opposed.
Ho delle perplessità.
I have some reservations / perplexities.
'Perplessità' (perplexity/reservation) — a sophisticated B2 term for doubts
Ci sono punti che mi lasciano dubbioso/a.
There are points that leave me doubtful.
'Lasciare dubbioso/a' (to leave me doubtful) — specific points generate the doubt
Non sono al cento percento.
I'm not one hundred percent (sure).
Casual — 'al cento percento' is a modern colloquial expression for full conviction
'Non torna' (it doesn't add up — literally 'it doesn't return') is an important Italian idiom for something that feels inconsistent or wrong. Italians use it frequently when something in an argument, account, or plan feels logically or ethically off.