Yes basically as Pepster64 suggested, the best way to help you learn Responsive design is using plain code and CSS Media Queries.
CSS Grid and Flexbox are the most common way of doing and the have huge flexibility on how you could use them.
You can try starting from a Mobile version of the website and scale up to Desktop, or vice versa.
The thing that I learned as I was coding and helped me tremendously, is that there is no specific break point for each website. You could try resizing the website and check the point that your layout breaks and it is the point that you could add a media queries to adjust it.
With this way it will work on all devices that it will use it.
That’s way frameworks and not always the best solution, because the have premade-break points like 768px for tablet etc.