Question: “If i don’t know what wrong karma i did in my previous lives then how can i correct my karma in present lives. Is there a way to understand past karmas in present lives.”
Not really. Until you’ve reached Enlightenment, you can’t “see” your past lives. Past Karma isn’t really as important as your present Karma. You should be more worried about your present and future Karma/life than your past, because there’s nothing you can do about it.
However, we can create a fairly general idea of any good/bad karma from our past lives in our present. Are you poor, comfortable, rich? Good looking, average, not good looking? Do you do well in academics, hobbies, or extracurricular activities? Are you better at something than something else? An odd talent or no talent? You can judge your present life and give a general assumption if past lives have done good or bad to create your good or bad present life. So even though (unless you’ve become liberated) you might not know your next life, it’s important to better it in this life. All our good and bad deeds/karma will affect us – either is this life, the next, or any future lives. So if you’re practicing Buddhism, or just practice a virtuous, good life, be happy to know that your next life will be much better, happier, healthier, and longer.
Smile and be well!