Get professional help, please don't follow any crazy diet unless supervised.
I would start with a fast walk everyday - try to do 10-12k steps a day. It is a lot, but if you walk fast for 45min/1hour it can easily be done.
Do some lightweight exercises at home if you can, lots of youtubers have 12 weeks plans for you to follow at home. Don't feell bad if you cannot do everything, do on your own pace and adjust if you cannot do something.
Don't give up, if you are obese it might take a while - there's a saying that goes: it takes 4 weeks for you to see some changes, 8weeks for your friends to see the changes, 12 weeks for the rest of the world to see the change.
Your main goal is to lose weight, but just cardio is not enough - weight training makes you burn more fat in the long run. Try some weight training before going for your walk, you'll keep burning.
Try to stick to a diet but nothing to crazy, no one can live off salad alone. I have one online personal trainer and she is the only one who has helped me get in shape over and over. She has a 3 month plan that it's not the cheapeast but it's so worth it, she knows what she is doing and it's very supportive. Her name is Randi Kennedy if this is something you might be interested.