I’ve noticed A LOT of Hindi speakers using the Latin alphabet to write and I even have a Bible that is Hindi written in the Latin script. Also an Urdu Latin Bible too. Is this some alternative unofficial way of writing or what?
From what I've seen and heard, it's common to text and type in Hindi with the Latin alphabet in informal use. The main reason is that a lot of technology companies have only recently begun adding Devanagari support to their products. Android only introduced a Devanagari keyboard in 2017. Even though most major operating systems now support Devanagari keyboards, it's not easy to find a laptop with an actual Devanagari keyboard. Options for Devanagari typing include Devanagari keyboard stickers, and softwares that convert Latin transliterations into Devanagari.
Outside of informal communications, the Latin alphabet is not commonly used. There are several standards for romanizing Devanagari. The most common ones are IAST (what Duolingo uses) and the Hunterian system. The Hunterian system is considered the official romanization system by the Indian government, although Hindi in Devanagari script is still considered the official language (along with English). These transliteration systems are mainly used for language learning materials and linguistics.
The informal use of Latin alphabet by Hindi speakers doesn't usually follow any standard system, and there's a lot of variation and inconsistency in how Hindi speakers romanize their language. Unlike most of the standard systems, Hindi speakers don't normally distinguish between letters like त and ट or अ and आ
That is not quite accurate. In spite of Latin and Sanskrit being both Indo-European, South Asian languages still developed far away from European ones, and converged more phonologically with Dravidian languages. We do not have Latin letters for the retroflex set of consonants, for example, which is why Polish orthography is... gestures vaguely like that.