Is it bad if i have anything with sugar right after my food?

Stop worrying: Refined sugar tastes good and people tend to overeat it, but the claims you've heard that it's a "terrible poison" are exaggerations. Eat sensibly and stay physically fit. Life's difficult enough without taking seriously every piece of lay "advice" from the internet. Best wishes.

Not per se: As long as you are not diabetic, having something sweet after food is not injurious to health. Try to keep your total sugar intake low and exercise regularly.