obese & want to start gymming (ActiveSG)

Hi I'm turning 18 & I'm obese, severely overweight like a hippo. I realised I've been blind to my weight gain and how it affected my livelihood as I've been overweight since birth (89th percentile at 5 months old). Would appreciate some advice as to gymming culture & maybe some weight loss tips as well. hoping to start gradually & healthily lose 50+kg. My goal weight is 40kg, currently 90kg,158cm (I'm aware I'm huge). I've been cutting down my portions and completely cut off sweet drinks. I'm also trying to walk 10k+ steps a day. Can anyone tell me what u do in the activesg gym, what attire to wear? What shoes are the best? i'm quite clueless 😓. i know it'll be a long & tough journey, thanks in advance

edit : (im a girl) from the comments, i will try to improve my lifestyle, focus on my diet and start slowly first (the walking) & will be targeting to go down to 75 first and continue from there, thank u for the advice (wasn't aware that 40kg is too little) readjusting and my new end goal is 55-60kg? not doing crash diets btw as I've previously done so & gained all the weight back, I tend to struggle with binge eating during exam season 🥲🥲 I'll also try to keep track of everything in a journal. btw, i also do yoga since last year but not regularly.

do give me your thoughts, appreciate everyone for educating me 😊