In my experience alot of machine learning is developed in Python(PyTorch) or Java. it may also be helpful to learn the C languages as well. If you happen to be focusing in any particular side of Machine Learning , I recommend looking at the website http://airesources.org/ . It is a huge database of machine learning and AI resources that includes data and code from various Machine Learning projects. It clearly organizes different types of Machine Learning and if you are focusing on a specific type, you can gather which language is used most often.