When I want to get fast times, I choose puzzles that have success rates of above 70%, and average times below 400 seconds, by clicking on the new game button. If you start with those, you won't get so frustrated.
There are only so many kinds of clues, and you will become faster at comprehending those. You will be faster if you skim the clues. Such as, instead of reading all of:
The scoutmaster who taught the half-hitch knot has an anniversary after Liam Neeson's cousin.
Just skim to get "half-hitch" "after" "Liam". Then, put your x's in the boxes.