Lauren's answer is the best way I can think of to go about it, but if for whatever reason you can't or don't want to do as she suggested:
A person who isn't a fully competent speaker of any language, like English, will normally carry over idiosyncrasies from "their" language. The main example I can give is that home-language speakers of Afrikaans, which uses only one word ("is", pronounced like the "iss" in "hiss") for both "is" and "are", very often use "is" and "are" inappropriately; some, because of the similarity between the English "is" and the Afrikaans "is", barely use "are" at all.
Another common slip-up I see with Afrikaans speakers is grammar, specifically word order. People tend to instinctively use the sentence structure used in their mother tongue, rather than that in the new language.
Unfortunately, I don't know anything whatsoever about Hindi, but I get the impression from what you wrote that you do know the language, at least to some degree. Look at the sentence structure and anything peculiar to the language, and use those as starting points. Although I wouldn't recommend using them as-is in dialogue, word-for-word direct translations of Hindi sentences would be a good way to find these idiosyncrasies.
One last note about word choice: The difference between a technically correct word and a situationally correct word is one of the last things someone learning a language grasps. Using not-quite-right words can be a good way to convey that someone doesn't speak a language well, while still making what they're saying fully comprehensible to your reader.
The first example that comes to mind is that while "He was driving very quick" conveys the same idea as "He was driving very fast," only one seems correct to an English speaker; not so to someone new to the language, who only knows the broad meaning of the words.