Learning Marathi through Hindi is very easy. Being conversant with Hindi has many advantages while learning Marathi.

1) Both languages use the same script i.e. Devanagari. So by default, you can read Marathi.
2) The beauty of Devanagari with respect to the Roman script is that the pronunciation is the same as what it is written. So you will not make mistake in pronunciation of Marathi words. So that part is automatically taken care of
3) Mostly the sentence formation rules (e.g. a sequence of the noun, verb etc.) in Marathi is the same as Hindi. So generally you map a Hindi sentence into Marathi word by word.

In short, you know Hindi means 80% you already know Marathi.
So in this coming lessons, we will try to cover up those 20% !!

In my blog for learning Marathi through English(http://kaushiklele-learnmarathi.blogspot.in)

I had explained grammar in detail. English is a completely different language, I thought it necessary to introduce a learner with grammar then slowly moving to simple sentences and then big conversations.

But as you know Hindi, I would directly start with Marathi sentences. You will be able to extract the grammar automatically. Wherever required I will explain the difference.
Also, many people who know Hindi want to grasp simple sentences quickly and develop their skills by more listening and reading. For them, learning grammar in detail is a discouraging factor.

So the approach is completely changing while learning Marathi from Hindi.
For some examples transliteration is given in Roman script is as well. This is for the convenience of search-ability on internet.

Conventions for writing Marathi/Hindi in Roman is given here

Vowels, Consonants in Marathi and their pronunciation
Marathi Barakahadi : Symbols for vowels with consonants

Those who can read Devanagari should ignore Roman transliteration as it may cause confusion.

So start learning Marathi. I am sure you will find this website very much useful. !!

You can master the pronunciation of Marathi by watching around 150 audio. video clips at my YouTube channel

List of all lessons can be found here
Learn Marathi From Hindi