what do you think, Which is the best code to start with & why?

Answer 1

'Hello world', because it is a good old tradition.

Answer 2

Try Fibonacci's sequence. It kind of tests your ability to use the most basic building blocks of a language you code it in. Plus it has plenty of coverage in lots of resources you can address if you find it difficult.

Answer 3

the calculator it has variables , functions , operators , operands yet its simple & fun