Hopefully this answer helps you.
The best way is to customize Bootstrap. Getting up to speed with Sass some time ago took me about 20 minutes. Trying to override color for color or style for style is time consuming and increases the time to get the project done.
I would recommend using Visual Studio Code to do your editing and working through the documentation. I have attached a picture of template folder (in the reference below) and the starting *.scss file that I use before each project that might help. There are two videos that can push you accross the finish line just in case. I hope this helps.
Reference - Customizing Bootstrap CSS