Hello!
First off, join one of the groups on here that support each other, here's a couple
https://www.mumsnet.com/Talk/weightlosss_chat/4094146-LOSE-IT-December-2020
https://www.mumsnet.com/Talk/weightlosss_chat/4097783-The-December-thread-Lose-7lbs-3kg-per-month
You can do exercise in your own home and there are loads of free programmes on YouTube or the OurParks website.
Weight loss is mainly about how much and what you eat though so I always recommend using an app like my fitness pal and a pair of scales to log everything you eat and drink.
I've been doing that since 1st August and have lost 3 and a half stone from 16st 9 to 13st 2. At my highest I have been around 20st when I was about your age, I'm 37 now.
Don't go into it all guns blazing and restrict your food so much you get miserable. You should aim initially for about 1600 calories and take the time to get used to what portion sizes look like.
I always find that reducing carbs helps, it stops my sugar levels spiking which stops the surges of hunger and craving for snacks, it also helps because carbs are high in calories so you can have more food on your plate if you swap them for good veg like green beans, baby corn, mushrooms, asparagus, broccoli, cauliflower... all of which are very low cal (a cup full of mushrooms is about 30 calories.
High fat and high protein will also fill you up for longer, so you can have a 2 egg omelette (med egg 65 cals) loaded with mushrooms, onions, peppers and a small amount of strong cheddar or larger amount of reduced fat cheddar for under 200 calories. 1 slice of whole grain bread is 120 calories without anything on it and won't keep you full for anywhere near the same amount of time.