How to have a flat stomach?

Ok, I need surefire ways to flatten my stomach. I've got ridiculous amounts of pudge and I'm sick of it.

I've been working on doing situps, although I sometimes think I don't do them right because I put a pillow behind me for my head.

But anyway.

PLEASE.

I need anything that can help. Exercises to do (with instructions, por favor) and anything..foods to eat, foods to avoid..

Whatever will help.

I'm joining a gym soon, but I really need to have a flat stomach in 9 months.

Please don't post any diet scams -.-

I need details, anything that will work. Thank you in advance<3
How to have a flat stomach?
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