I don’t think absolute numbers are very useful here. You need around 5–10% reduction in calorie intake to get any weight-loss effect going, and I wouldn’t reduce by more than 20% (relative to weight-maintaining intake — it’s different if you’ve been seriously overeating) if you want it to be sustainable longer-term.

So for example if your weight is stable at 2500 kcal per day, I would start by reducing the intake by 250–500 kcal, but not more. If this works well for a month or two and then you want to lose weight faster, you can still reduce your intake further. You generally have to do that anyway even just to maintain the velocity, because weight loss also tends to reduce calorie expenditure.

First and foremost, you need to monitor your calorie intake against weight. Here is a useful text about that: https://www.fourmilab.ch/hackdiet/