Python is the first language that I have learnt. How should I proceed next?
It completely depends on what you want to achieve. My personal advice is to know Python stack deeply to be able to solve any problem on it rather than focusing on more languages to learn.
If you know Python well, there is no problem which can not be solved in Python. If you still insist on learning a new language - Java, Scala, Julia, SAS and R are all worthy contendors depending on what you want to achieve.
If you want to get into traditional Business analytics and predictive modeling - SAS / R might be a better choice. However, if you are working on big data / scalable problems, Java / Scala / Julia can all be good choices.
Hope this helps.