The months of the Gregorian calendar (which is used for most secular purposes in India) are given names derived from English - जनवरी, फ़रवरी, मार्च, अप्रैल, मई, जून, जुलाई, अगस्त, सितम्बर, अक्टूबर, नवंबर, दिसंबर. Note that even though they are derived from English, the pronunciations of most of them are different from the English pronunciations.
The months of the Hindu calendars (which are today mostly used only for religious purposes) are given names derived from Sanskrit - चैत्र, बैसाख, ज्येष्ठ, आषाढ़, सावन, भादों, अश्विन, कार्तिक, मार्गशीर्ष, पौष, माघ, फाल्गुन. Note that the same names are used for the months of multiple Hindu calendars so the definition of these months will vary regionally. Sometimes, the names of the 12 zodiac signs in Hindu astrology are also used as names of months.
The letter र (r) is combined specially with other letters. If the simbol is above the letter, it means you pronounce the 'r' sound before the letter. If the simbol is below, your pronounce it after. Examples: र् + क = र्क as in ''sark'' सर्क
क् + र = क्र as in ''cross'' क्राॅस
Another related letter is ऋ (ri). When combined with another letter it looks like this:
कृपया (kripya = please,kindly).