Almost every language has an MVC framework available, if you learn one a lot of the terminology and concepts will be the same in others. For Python, Django is the most popular one. You should start there and learn how to make something without involving JS then once you become comfortable with the backend you can add a frontend JavaScript framework like Angular, React, Vue, etc.
If you go the JavaScript route, you only need to learn one language. Check out <a href="https://www.freecodecamp.org/" rel="nofollow">https://www.freecodecamp.org/</a>.
Pick a stack for back and frontend, stay with it, and get good instead of jumping around constantly. Doing otherwise will slowly put you behind, and you will have to work pointlessly hard.