Should I learn only One language at a time or I can continue with python+Java+etc

Answer 1

I did them all together but I have a background in programming. However I would suggest you to stick with one. Finish it and then move to the next.
Good luck.

Answer 2

Better to master one. If you master Java you can move to lets say c# quite easily.

Answer 3

With that said, once you know one, the rest are easier to learn and at a certain point you can learn any number at a time because it's really just syntax you're learning then (for the most part). On the first one, you need to learn the skill of Programming which takes time and a bit more focus.