so i just threw that together as an answer for someones question but i thought hey why not make it a take for everyone. i don't have a formal education or degree in the field so if you do and find something that is complete bullshit please correct me in the comments.
to save you the hassle of reading all of this:
tl;dr: Work out, eat less calories (not less than 1800) and most importantly: cut carbs and sugar. don't cut fat. fat is good. realize that you have to do all that for probably 2-3 years. you can speed it up by working out harder but never cut your calories to less than 1800 per day. eat stuff that has little calories per gram.
so most ignorant morons (as i was one not too long ago) will tell you to "just count calories and work out"while that is surely one thing you should most definitely also do, it's "probably" not the most important thing so i won't make this take. about workout. there's surely more than enough resources for that.
i found the most important thing by far is to change your diet. not only calories matter but also what calories.
if you're fat, what comes to mind first is: well eat less fat right? wrong. being scared of fat is the first fatal flaw of any diet. your body loves fat and the last thing it wants is to let the valuable reserve go to waste. so your body will litterally rather burn your muscles and even burn superflous parts of your own organs before it will burn your fat. if you don't eat fat anymore, your body is like "oh shit we're not getting any fat, so i should probably try even harder to store what fat i already have". so in conclusion: you want to eat fat. fat is good. however try and go for poly-unsaturated fats as much as possible. the more your body is used to burning fat in general, the easier it is to burn fat reserves. don't overdo it though, cause fat is super calorie dense. counting calories is still important.
the second fatal flaw is undereating. yes you can undereat. sure not eating at all will make things go a LOT faster but well that's much harder and shouldn't be done without the help of a doctor as it is dangerous and unhealthy. i'm speaking unscientifically now but your body has something you could call a "emergency starvation mode". it can considerably cut down on calory consumption so if you eat too little calories, your body will switch to burning way less calories than usual. so unless you're doing the "not eating at all" thing with the help of a doctor, never eat below 1800 calories so your body doesn't switch to emergency mode. in order to feel full despite eating little calories, eat stuff that has little calories per gram. for example you can eat an entire bag of frozen vegetables and still have eaten less calories than a chocolate bar. a good rule of thumb is less than 100cal per 100gram is good. more than 100cal per 100 gram is bad (fat will violate that rule but i already explained why you still want fat).
so now you know your body does everything not to burn fat. however the third thing (which is probably even more important than the first) is sugar and carbs. some diets tell you carbs are good, cause it is harder to break down but well carbs are metabolized into sugar either way and sugar raises insulin levels. high insulin levels in your blood litterally block the biomechanics that are at work to break down your stored fat into energy so you litterally are unable to burn your fat. if you eat few calories with sugar and carbs, you're starving your body, cause it doesn't get enough energy and can not burn the reserve it has making your weight loss journy miserable.
last but litterally not least: it will take a long ass time (i'm talking years). don't give up if you have a set back. it is ok to cheat your diet once in a while. even if you have a breakdown and overeat/violate your dietary rules for a week or so, don't give up. realize it was a mistake. get back on track. setbacks and weakness are ok. giving up is not.