I agree with other answers which state that knowing some terminology and vocabulary is useful, but learning the grammar is unnecessary, unless you're a scholar. The reason is that some words are technical terms with specific meanings, that can't be easily translated to plain English words.
While there's no need to know the grammar, it may be useful to be able to separate words from their inflection (e.g. noun declension and verb conjugation), so that you can refer to them in a dictionary or glossary.
Here's an example:
From AN 10.58 (translated by Bhikkhu Sujato):
Reverends, all things are rooted in desire.
chandamūlakā, āvuso, sabbe dhammā
Initially, when reading only the English translation, you might wonder what "things" are, and what "desire" is. Probably, this is related to the second noble truth, which states that the cause of suffering is craving.
But if you look at the Pali words here, we find that "thing" refers to "dhamma" and "desire" refers to "chanda".
The word "dhamma" has many meanings as can be seen in this answer.
The word "chanda" for desire, is different from the word "tanha" for craving (of the second noble truth). Please also see "Difference between desire (chanda) and craving (tanha)?". These are technical terms.
So, this phrase doesn't refer to craving.
But it was not clear to me what "things" refer to, so I created this question.
By the way, the "ā" in "dhammā" for "dhamma" (thing), is the declension to indicate that it's plural i.e. "things", but we can leave that detail to the translator, though it's useful to extract the basic word so that we can refer to it in a dictionary or glossary.