You've spawned a silly thread, because mastering a language is a spectrum that takes years.
In 3 days someone should be able to fix a small business logic bug in a program in a new language, like copy-pasting a if-block to handle a new simple case, or improving an error message by grabbing a variable from context and for setting it for output, but not write a useful program.
In 3 days someone should be able to fix a small business logic bug in a program in a new language, like copy-pasting a if-block to handle a new simple case, or improving an error message by grabbing a variable from context and for setting it for output, but not write a useful program.