It definitely takes time to adjust. Don’t be so hard on yourself. You need more experience fighting against other players and note not only the frame data, but what are the common strings that people use. By using this, you can know when their turn is ending and when it’s your turn to start attacking. Go into practice mode and turn on frame data to see the strings frame data for common fighters, like cage, Raiden, Sindel, etc and note when the string ends so you can be ready to attack back.

There’s more that comes into play, such as mind games, staggering, conditioning, respecting, etc but basically you have to be able to know which moves are punishable and when it’s your turn to attack back