First my home has lots of food from chips, cookies, soda to you name it unhealthy food.
As has been said, you don't have to eat the stuff. Or, eat less of the stuff. Keeping track of what you eat is good - turns weight loss into a mathematical and logical puzzle that can be solved, rather than an emotional and psychological struggle. You'll know when you can eat an extra cookie, or you can understand why the scale doesn't move in the direction you want if you eat a bit too much.
Second people around me is not supportive, when i try eating small portions of food they laugh at me and says "stop trying".
Yeah, this part is probably the toughest. I never really got around to trying to lose weight until I was out in college on my own, so it was easier. My family wasn't necessarily unsupportive, but they weren't necessarily supportive either. I'm just the type of person who has to do it on his own. For me, support was demotivating when I was starting out, while I was motivated to prove someone wrong if they say it can't be done. Once I started seeing progress, I started liking support more, but somtimes it gets annoying to be the center of attention and tell people how you did it ("what pills did you take?") and listen to them say how good you look (what, I didn't look good before? gee thanks. You're right, I was pretty fat!")
Its hard, but just ignore the comments, do what you have to do. Eventually the comments will stop. Probably once the people around you see progress. The comments may be out of hate or jealosy, but possibly also if it looks like a struggle or like you're starving yourself, they could just be looking out for you too. Hard to say without knowing a little more. Arm yourself with a bunch of knowledge, and the next time someone says something that bothers you, explain what you're doing, and why you're doing it. Explain your plan, explain why it will work, explain you're not torturing or starving yourself to do it. Tell them you would like their support, and if they won't give it to you, you'd rather them not say anything about it at all. If they're worried about your health, offer to go to a doctor to explain your plan and get their opinion. If the people around you truly care about you, they will help you. They might just not understand right now, but you can help them understand.
Second i have a bad knee, all i can do is walk slowly. I can't run or jump. I can't exercise or workout hard. There is a steam bath near in my house but i don't know if that can help. If you're me what do you think should you do?
First, if you haven't already, go see a doctor for your knee. Find out exactly whats wrong, and what you can do to fix it. Some problems can be fixed with physical therapy. Leg extensions strengthen the muscles around your knee which can fix some knee problems, but don't try to do anything until you've seen a doctor.
While you're working on that, there are still exercises you can do. Cycling is low impact on the knee for cardio. If even that is too much, you can do rows. You can do weight lifting for your upper body at least, and maybe some exercises for your lower body that don't put a lot of strain on your knee. You can do body weight exercises like pushups/situps/inverted rows.
However, all that being said, you can lose weight without doing any exercise at all, just by controlling your food. Its a lot tougher, and you don't get any of the other benefits of exercising, but it can be done.
