Hi again Sergio!
That's a very understandable (and I imagine frustrating) situation. There's nothing wrong with starting with a higher timer and gradually working your way down! You can always start with 60 or even 90 seconds, see how much you get done and practice this regularly for 1-2 weeks. If you feel more confident, lower the timer one step down (so if you did 90 seconds, go down to 60).
Alternatively you can practice to draw faster, too. A quick stroke with some disregard for perfection/detail is what gestures are about, after all! The circle and vertical/horizontal lines should be easily done in about 5 seconds, giving you 25 seconds to draw the face shape and other features. (You can also leave out the circle entirely and just work from the vertical and horizontal lines, but this is personal preference for sure.) Your goal is not to be perfect but to get a feel for proportion and train your brain to recognize what it sees and put it down on paper in the simplest way possible, while keeping the expression intact.
In short, you're trying to figure out the essential key features in a face that determine the expression and emotions. Arched eyebrows with wide eyes can convey all the surprise without needing a nose and mouth and jaw/face outline, after all! Being able to recognize these key features and jotting them down quickly as a base is something to work towards alongside finding the right proportions.
You can definitely combine a bigger timer with practice for quicker sketching. Both work just as well and will help you improve, but you may need to experiment to see what works best for you.