To improve your weaknesses you first need to know them, you may have flaws and not even realize. First you need to evaluate yourself, ask yourself a few questions such as listing down 2 things you think you are good at, 2 things you can be depended on for and 2 things you need to improve.  By doing this you're setting up a foundation to understand yourself better, you can list more than 2 things for each section as well but 2 minimum. 

Now that you have that part done, you need to do some further research about yourself,how can you do that you may ask? Well who knows yourself best after you? It is usually close friends, family and colleagues. Reach out to 3-5 people and ask them the same questions to evaluate you, you can let them know you're doing self reflection and need an honest breakdown. This can be done in person, email, paper, text whatever works best for you. 

Once you have received feedback now it is time to compare the results to get a better understanding of yourself. Look if there are any similarities between your strengths and weaknesses from these results, this should show what you need to improve. Now it's time to set goals, set short term and long term how you can work on and improve each weakness. Stay consistent with those goals and work towards them and in a few months reevaluate yourself to see the progress.

Don't limit yourself, make sure to keep working hard to better yourself, to learn, to stay updated there will always be something for you to conquer no one is perfect.