"dim understanding" is correct and usable in written English.
You can use it to describe a vague, limited, or partial comprehension of something. For example, "My dim understanding of the subject made it difficult to understand the entire lecture."
And it feigns a young girl's dim understanding of what has happened.
Everyone has a terrible memory and a dim understanding of consequences.
Scientists have only a dim understanding of how the system decides which to kill and which to tolerate.
Ben Sapers, a 33-year-old primary-care doctor who completed his training last summer, said such concern reflects a dim understanding of medical education today.
It shows not even a dim understanding that millions and millions of people feel heartbroken by this election and what it revealed about America, and may want to come together for solace.
Thanks to strenuous efforts by the Communist Party to erase memories of what happened (see article), many in China now have only a dim understanding of the history of the protests in Tiananmen Square and the nationwide unrest they triggered.
Larry is too dull, dim-witted, and devoid of any basic understanding of physics to realize that the snow will melt inside the hot truck.
"It was to some extent informed by my years in Indonesia, seeing extreme poverty and disparities of wealth and understanding sort of in a dim way that life wasn't fair and government had something to do with it.
Dim light conditions may allow a better understanding of daily events taking place in an organism in response to light.
11. "Feeling like you don't really belong anywhere and not understanding how some people can be so vapid, shallow and dim".
This undercounting, of cool, dim dwarf stars in certain galaxies, could throw a monkey wrench into astronomers' understanding of how galaxies formed and grew over the eons.
