Which one is better for mechanical Engineer stream. What language should learn first.

Answer 1

C is recommended :)

https://www.asme.org/topics-resources/content/c-as-part-of-a-mechanical-engineering-curriculum

Answer 2

If you are not coming from computer field then python is best for you. It is easiest language. You can start course here or there are many YouTube channels from which you can learn python.