First, I deleted the source and link to the espresso machine. Apologies, but it is not needed for this discussion. Anyway...
In my opinion, you can be going down a very deep rabbit hole here. Personally, in my opinion, a good espresso can be obtained by the use of a good cafe that has a good barista ...
But, if you must do it yourself ... people has spent lots and lots of money and time to get the perfect brew. On the
coffee side, it can highly depend on the bean, the roast, and the grind. And on the brewing side, it can highly depend on the
water source, temperature, and time of brew.
I guess, if you want to improve, some possibilities are (which my brother explained to me years ago)...
1. Don't skimp on the quality of the coffee bean. And especially, don't use old coffee beans.
2. Get you own grinder, as you may want to try out different coarseness of grinds.
3. Use a good water source, or good filtration system.
4. Use a good machine that can maintain a consistent (and possibly controllable) temperature.
5. As for brew time, I guess you need to constantly
test it. Different coffee beans and grinds actually affect the brew time, so not only do you need to find the optimum time, but you may also need to check it now and then, when you get a new batch of beans (or grind it differently).
Henry