@atheistone Right now, according to
https://tdeecalculator.net/, your maintenance calories at sedentary are around 1,700.
1,200 calories is the absolute lowest anyone should ever go and is often very difficult to maintain over a long period of time and ensure proper nutrition. If you aim for a calorie deficit between 250 - 300 a day (so 1,400 calories a day), you can lose a KG a month, which is sustainable goal that allows you to change your lifestyle eating and moving habits so that the weight stays off and you stay healthier.
The 10,000 steps rule has been largely discredited (
https://www.theguardian.com/lifeand...-the-10000-daily-goal-is-built-on-bad-science) but walking is always an excellent choice for better health. Introducing as much passive walking to your lifestyle as possible (walk to / from work, to / from store, etc.) is helpful. Working on walking faster and longer is also great. Generally, brisk walking has a burn rate of @ 3 calories a minute. Maybe the more you move the more interested you'll become in moving more: hiking, biking, running, etc.
I would give yourself two years to lose 25kg. That may seem disheartening, but if you're looking for a fast and temporary solution you'll just put the weight right back on faster than you lost it. Maybe set a whole bunch a smaller milestones along the way and focus not so much on the scale but on how you look and feel and, most importantly how you eat and move. Learning to eat healthier and move more as just integral to your everyday life will set you up for a lifetime of good habits!
Good luck - you got this!