its awesome that your working on your fitness journey!
to start, i would follow the 80/20 rule. lots of fitness gurus follow this rule. the 80/20 rule is that you eat healthy around 80% of the day and have 20% of some sweets, or processed food. i've been following this rule, and its awesome, sometimes i dont even feel like eating that full 20%.
lots of cardio is needed to shred fat! doing HIIT is awesome, because you still burn calories long after your workout. i would suggest lota of hiit and lots of ab work!
best of luck ☺