You need to seek advice from someone who can provide exercises to strengthen specific areas to retrain your posture.

Your rounded shoulder are probably due to tightness in the pecs and a weakness in the back muscles. So to correct you would need to strenthen up your scapular stabilisers and stretch out your pecs. One without the other will probably not work.

Your forward head posture is probably due to a lack of muscle stregth at the back of the neck, causing you to rest on your ligaments and poke your chin

Hope this helps a little. But changing your posture is not a quick thing to do. You will nee to put a lot of work into it to achieve your end goal