Why understanding Sanskrit does not help in understanding the Upanisads

The knowledge of the Upanisads go much deeper than mere grammatical understanding.

The verses of Upanisads often describe large volumes of information in just a few words. There are often verses with just 14 or 16 words describing whole branches of knowledge. This makes it practically impossible to understand the Upanisads without learning them from someone (or having access to some really good explanations) or by knowing the topics and conclusions discussed in the verses beforehand. The word “upa” means to come close, “ni” to sit, and “shad” to learn. These are books meant to be studied under a spiritual teacher. Even understanding Sanskrit does not help much. Take for example this verse from the Mundaka Upanisad (2.1.8):

sapta-prāṇāḥ prabhavanti tasmāt
saptārciṣaḥ samidhaḥ sapta homāḥ
sapta ime lokā yeṣu caranti prāṇā
guhāśayā nihitāḥ sapta sapta

A literal translation would be:

"From that (Brahman) arise the seven vital energies, the seven flames, the seven fuels, and the seven sacrifices. These are the seven worlds in which the life forces move, positioned in the cave (of the heart) in groups of seven."

However, the translation does not help much in understanding the meaning.

This verse explores the concept of the seven to describe how we perceive reality in this world, and how all of this comes from the Lord. He creates not only the material world but also the senses by which we perceive it.

According to Srila Madhvācārya, "sapta lokāḥ" means the seven senses organs (tongue, two eyes, two ears, and two nostrils) and "sapta prāṇāḥ" the seven vital airs that sustain them. "Sapta-arciṣaḥ" (seven flames) indicate their capacity of perception, "samidhaḥ" indicates their "fuel", or source of support, which are the objects of the senses. "Sapta homāḥ" means the perception of these sense objects, or how they are perceived by consciousness.

In the philosophy of Lord Kapila, explained in the 3rd canto of Srimad Bhagavatam, five functional senses are counted, but in the 11th canto Krishna explains that the material elements (including the material senses) can be counted in different ways, therefore there is no contradiction with the current verse. In other explanations, there are five knowledge-acquiring senses and five vital airs, but because here the senses are counted in a different way, the counting of the vital airs that maintain them, the objects of the senses, etc. also follow.

"Sapta lokāḥ" also means the seven planes, or the realms of existence in the material world, which are explored by the souls using their senses. The soul itself resides (caranti) in the cavity of the heart (guhā), covered by seven coverings (starting with material consciousness and false ego and culminating with the gross body) floats in the subtle vital airs (prāṇāḥ).

In each of the seven words, or seven divisions of existence, the same seven-fold division is present, or in other words, everywhere souls assume bodies and senses and try to enjoy the material nature in a similar way.

In this way, there are thus seven divisions of seven (sapta sapta), and the Lord is the master of all these divisions. These divisions were created by Him in order for us to acquire knowledge and realize our eternal relationship with Him.