Plenty of diet recommendations, some might work, some don't.

Most important though is: eat less calories than what you need. Calory counting basically. You can keep eating what you want, as long as it is less than what your body needs.

Aggressively, while still being healthy, would be: eat 1200 kcal while an average man usually needs 2000 kcal, daily.

There are apps to track this. In the US, I've found this one to be very userfriendly: https://www.myfitnesspal.com/. E.g. you can just scan the bar codes of most of the products you consume.