So I would suggest two! Learn backend dev or deep learning using python.
I recently started a new job and we use python for machine learning and our backend systems. It was really easy to pick up, but I had a background in PHP backend. Now I am not in the ML team so I haven't learned too much about it - I will peek at the code and understand it a little but I enjoy the backend written in python.
So I would learn 2 at a time, learn how to develop a backend in python. Then you walk away understanding how backend development works and you can apply other languages you may know to the concepts, as well as understanding python more and you can then apply that to other applications outside of backend.