There is no agreed system. The same word appears as kya, kyaa and kyā. Worse, Hindi has sound distinctions English has no letters for:
Learn from roman script and you learn the wrong sounds, confidently, and have to unlearn them later. Unlearning takes far longer than two weeks.
Devanagari is an alphabet with a consistent logic, not a set of thousands of symbols. Each consonant carries a built-in "a" sound, and vowel marks change it. Once the pattern clicks, the rest follows fast. Most learners read slowly but accurately within two weeks.
Compare that to Mandarin, where literacy is a multi-year project. Two weeks is nothing.
A trip in six weeks and you only want to speak. Then yes — skip the script, learn phrases, go. That is a different goal, and a sensible one.
For anyone learning Hindi over months rather than weeks, the script pays for itself well before month three.
Our free guides begin with the alphabet, and this page explains how the letters are organised — which is the part that makes it click.
Reading an answer is one thing; being corrected while you say it is another. EkGuru tutors teach one to one from $6 a lesson, and most offer a trial.