Python : Python Tutorial - Python for Beginners [Full Course] : https://www.youtube.com/watch?v=_uQrJ0TkZlc
DSA : Data Structures and Algorithm : https://practice.geeksforgeeks.org/courses/dsa-self-paced
R : Data Science : https://www.edx.org/course/data-science-r-basics
ML : Machine Learning : https://www.coursera.org/learn/machine-learning