You absolutely can change your personality - for the better or for the worse - and it's still going to be you. Pay attention to people and you will see that they change with time. We all can improve and evolve our soul, just as we can do with our body.
In 1788, Adolph Franz Friedrich Ludwig Freiherr Knigge wrote "about getting along with people", which is an actually (even today!) useful work broken down into different sections for different kinds of people, revolving around suggestions for topics which are likely to lead to interesting conversations with them.
In the 20th and 21st centuries, the name "Knigge" has been plastered all over various attempts at bog-standard etiquette manuals.
https://www.deutschestextarchiv.de/book/show/knigge_umgang01...