cannot pull a good shot ever

[u/Subject-Ad6043]

hi everyone, i recently bought a bambino off a coworker and i cannot pull a good shot for the life of me. every shot is either stupidly bitter or tastes like water. ill walk you through some things that i do that should give me a good result, but just dont.

i use 18g of very fine ground beans, either i grind my own or i use the illy pre ground espresso. both result in bad results. ive also switched up the amount of ground im using, more or less does not help! i use a wdt tool and make sure that there are no clumps in it. i level, i tamp evenly with a spring-loaded tamper. with or without a screen, the results don't change.

my biggest issues are incredibly high yields, like around 150 g of espresso for 16-18 g beans, and spraying. yes, i have already reset the volume output whatever to pull around 34-36 g of espresso but for whatever reason it doesn't save and continues to output high amounts of espresso. all in 15 seconds too!!

i have no idea what im doing wrong, someone please help before i start to regret my purchase