First, like everyone has said, don't snack on shit food. If you want to have an F1 super car you have to give it high quality fuel, same goes for your body. If you want to look good you have to give it quality food.
You can't do anything about the parents food, but you can stay away from crappy food outside of that.
Other than that the key is literally to out work your diet. I agree with everyone else yoy need to be active outside of gym time--the most successful people are people who are active in their daily lives, not just the gym. The gym is your biggest tool to succeed sure, but you have 23 other hours in every day that you should make work towards your goal to make it happen faster. walk, bike, hike trails, swim, do outdoors fun stuff. Shit, play disc golf.
regarding your gym time: Skip arms. When speaking specifically of the time spent in the gym and its effect on fat loss and muscle, the goal is to work as much of your body at one time as you can. The more muscles you work the more calories you burn.
Biceps and triceps are small ass muscles compared to your whole back or your legs. You burn far less calories doing a whole day of arms or even shoulders than with legs, or back.
So, split your training into one of the following:
whole body every gym workout (this means going 3-4 times a week, spread out, instead of 5)
The key to leaning down quickly while im the gym is to do more whole body lifts and lifts involved lots of muscles at the same time, instead of isolation stuff.
Do 50 minutes of compound exercises, and the last 10 minutes of each workout can be isolation stuff.
For added effect start to decrease rest intervals.