Edit: https://en.wikipedia.org/wiki/Reading_compreh...

Reading comprehension is the ability to read text, process it, and understand its meaning.

I assume that's what's meant by the OP's "sinnerfassend."

I agree with @dude.

Although LEO translates gist as Hauptinhalt, at least in AE gist implies catching the general sense of something perceived, but likely not perceiving or grasping the finer details of the subject at hand.

So, as @dude said, a more precise word would be comprehensive, which interestingly is both the adjective for comprehend or understand but also means umfassend and so implies much more than merely catching the gist of something. An example for the word gist:

or not capable/incapable of grasping

However, it is called reading comprehension / comprehensive reading

Definition found on google:

 

More context might help judge what slant is intended by the writer.

 

I suspect this refers to a score below level 1 on  the PISA test for reading literacy, which tests the ability of "understanding, using, reflecting on and engaging with written texts in order to achieve one's goals ...", possibly involving more than just comprehension.  It may also be relevant that the test measures comprehension etc. for texts in a specific language (presumably German, not Farsi or Arabic).