na in hindi
I think the "na with the dot underneath" is said incorrectly.
Refer to this discussion https://forum.duolingo.com/comment/28718087 about the pronunciation of ण and न. The argument seems to be that many speakers use न and ण as allophones and that ण exists mostly in Tatsam words in Hindi.
Personally, as a native speaker, I think the correct pronunciation of ण is absolutely essential not only in words like प्राण, प्राणी, बाण etc which contain ण but also in words containing anusvar such as पंडित or झंडा. The use of the न pronunciation in any of these words would sound wrong to me but to each their own.
I agree with you about पंडित and झंडा. In fact, they would more accurately be written as पण्डित and झण्डा but modern Hindi likes to replace usage of ङ् ञ् ण् न् म् with anusvar ं or chandrabindu ँ. Note that ङ् ञ् are not even used in Hindi but ण् न् म् are still widely used.
True. But even if the word is written with the anusvaar, the pronunciation would remain that of ङ् ञ् ण् न् म् depending on the following letter. This is because that is the natural pronunciation that results in moving your tongue the least between the anusvar and the following consonant.
It is not really necessary to worry about it at all, unless you are interested the linguistics. Our ancestors used a different letter to express the ण sound because that specificity and accuracy was important to them, but in words like पंडित (पण्डित), one does not have to choose to pronounce the nasal consonant in that way. It simply happens naturally when it's combined with the following retroflex consonant.
Similarly, the न comes naturally when combined with a dental consonant.
And so on.
This is how English get's by with one "n" which can be pronounced so different in "went" and "wing." In Japanese, one letter ん can play these roles and also be the "m" in a word like "kampai" (乾杯 = かんぱい).