I have doubt that whether the following sentence is correct or not:
Anytime my teacher was teaching the lesson, I was misunderstanding some notable points.
Actually, I want to use this sentence in a formal text. Is it the correct way to use "misunderstand" in a Past Continuous Tense form, given that I didn't see something like this. Besides, is "misunderstand" a suitable word for a formal text?
The sentence is grammatically correct but not idiomatic.
Firstly: Yes, misunderstand is perfectly acceptable in a formal text.
However, the use of the past continuous is very non-idiomatic here. We normally use a continuous tense to mean something like "to be in the middle of performing an ongoing action". But "misunderstanding" is not really an action you can be in the middle of doing.
For example, this would be idiomatic:
Every time the teacher called on me, I was daydreaming about baseball.
"was daydreaming" makes sense because to daydream could be a lengthy action that you were in the middle of when the teacher called on you. But "to misunderstand" is not something that you were in the middle of doing when the teacher was teaching the lesson. So
...I misunderstood some notable points.
is much more fluent. Actually, to be even more fluent, the beginning of the sentence should be
Any time my teacher taught a lesson...
because we're talking about a recurring or regular action (your teacher teaches a lesson and you misunderstand) and not something that happened in the middle of your teacher being in the action of teaching.
I don't feel that past continuous tense is needed for the word 'misunderstanding' because you already establish the tense by stating that this occurred "anytime my teacher was teaching", so you don't need to do it again. Saying that you were 'misunderstanding' during the lesson implies that from the moment the lesson began to the moment it ended you were in a state of misunderstanding. Actually you just 'misunderstood' some notable points.
Also, as 'anytime' sounds like it refers to multiple occasions I would say that "taught a lesson" is correct, as "the lesson" refers to a specific lesson (unless your intention is to state that you attended the exact same lesson that was being repeated on multiple occasions).
I would therefore express this as:
Anytime my teacher taught a lesson I misunderstood some notable points.
This shows that you regularly misunderstood some points during many lessons.
"Understand" is one of those verbs that doesn't work in the continuous. You can either understand it or not understand it, but you can't really be understanding it, as a continuous action.
In such cases we generally use a process verb of some kind to better explain what's going on:
I was trying to understand what he was doing.
I could see that she was failing to understand what I meant.
This also applies to similar words like comprehend, apprehend, discern, interpret, etc. as well as its antonyms like misunderstand, misapprehend, misread, etc.
Note: Don't confuse the continuous verb form with the noun misunderstanding:
They fought for hours but eventually agreed it had all been just a misunderstanding.
