Should I start learning Kotlin?

Question

Kotlin

I apologize in advance for clogging the forum with such questions, but for the third day I can’t decide, so I would like to ask more experienced developers.

Learned about languages ​​and technologies like Dart with flutter, Golang and Kotlin.
I don't want to run from language to language, I want to choose one and become a professional in it, and these languages ​​are now in my head and I can't decide to choose only one.

Tell me, is it worth completely switching attention to Kotlin? Or is Golang better?
(PS I tried to write on both, and liked both).

Answer 1

A professional knows many languages, and several in depth.
It is worth choosing one when you are at least a junior in 2-3

Answer 2

Missing array dimension in function.

Answer 3

What am I doing wrong ?

for(int i2=(sizeof mas/sizeof mas[0]-1);i2>=0;i2--){
if(mas[i2]>mas[i2-1]){

What happens in the if condition and further in the loop when i2 == 0?