この場合だと私なら I can't get my head around...と言うと思います。
例えば、I can't get my head around all the different usages of 'take' 。
I can't get my head around the meaning of this word. というふうにも使えます。
Can't get my head around ... = 〜が理解できない/理解するのが難しい。否定で使うのが一般的です。
I can't get my head around how to use this word.
I can't get my head around how to properly use 'take'.
〜のコアイメージが掴めない - I can't get my head around the core meaning of ...