How do I actually start losing weight?

As someone who’s never been really active, how do I actually lose weight? I didn’t really do sports in school, most exercise I get is swimming in oceans which I only get to do a few times a year. Simple exercises tire me out so much. I’m currently 60kg and I’m 5ft. I want to lose weight and reach probably around 47-50kg.

I’m on day 4 of trying to do a calorie deficit but it’s so hard to keep track of the calories I consume. Just now, I subconsciously ordered a sweet drink and completely forgot that I need to restrain and remind myself not to eat or drink sweets.

Any tips?(Gym advice is appreciated since I’m trying to get over my fear of getting judged at the gym and not knowing where to start)