how can I stay but still eat junk food?????

Question

You can stay healthy by eating mostly healthy foods and much smaller amounts of junk food.

That depends upon how much junk fund you want to eat. In general, however, eating junk food and staying slim (I suppose that is the word omitted) is possible but not probable. I have a lot of personal experience at losing weight (my weight was like a yo yo for years) so I know how to lose it and how to gain it. Three main points to losing weight. I will list them is order of how important I think they are:
1. portion control. I think this is the MOST important. 1/2 cup of most vegetables (1 cup if raw) is a serving, 3-4 oz meat is a serving, and 1 cup cooked pasta is a serving. Salads are low calorie IF they are not drenched in a high calorie dressing.
2. Don't skip meals. Eat three meals a day.
3. Don't snack (or if you do, build that into your eating schedule and save a few calories here and there to make up for the snack calories).
4.(bonus) Read the labels. I watch the fat content. Those frozen dishes I can buy at the supermarket that are over 8 g fat content on the label are a no no for me.
Depending upon your frame and your height, calories are adjustable. For me, I try to stick to about 2000 calories a day. And it works. My weight is 150, I walk two miles a day (every day), my weight has been 150 +/- 2 lbs for the past four years. I am 5'9" and male.
I eat a hamburger once in a blue moon, I will have a pizza once or twice a year, and I go out to eat regularly. Most restuarants serve too much food so the first thing I do is separate the food into two halves. One half I eat there and the other half I ask for a take-home for my next meal. There are other tricks I have (such as giving myself a reward when I've been a good boy) but you don't want a book for an answer. I hope this is useful.