I usually take a long time to process sentences even though I know all the grammar and vocabulary in said sentence. I still need like 5 seconds to grasp the sentence after reading it, And then I read the sentence again to just make sure my understanding is correct.
I usually take a lot longer in sentences containing particles such as の and に.
And God forbids I see こと in a sentence or a relative clause, In such cases I’d need to read the sentence around 4 times to just get it’s meaning