Reviews of the Melitta Molino indicate that the unit is not actually capable of achieving the very fine grind needed for espresso. Sorry to be the bearer of bad news.

Espresso grinders require very tight tolerances in manufacturing to enable the close proximity of burrs required for very fine grinding. This is why the vast majority of grinders made by reputable companies and advertised as "for espresso" tend to start in the several hundreds of dollars range. There's unfortunately no way to shortcut this requirement; loose tolerances would result in too many units being returned when burrs lock up from touching or people complaining that the grind isn't consistent enough. You might sometimes get decent results from cheap grinders, but cheaper grinders will lack consistency and may not be able to achieve very fine grinds at all with some beans.

Unfortunately the cheapest grinder I would recommend for espresso is the Eureka Mignon Filtro, which is generally priced in the US at $210. Also, the vast majority of grinders that grind well for espresso cannot grind well at coarser grind settings, so you'll likely want a separate grinder if you use other brew methods. Your Melitta should be ok for Aeropress, drip, and maybe French Press (not sure at that level of coarseness), so it's not a waste.

Reviews of the Melitta Molino indicate that the unit is not actually capable of achieving the very fine grind needed for espresso. Sorry to be the bearer of bad news.

Espresso grinders require very tight tolerances in manufacturing to enable the close proximity of burrs required for very fine grinding. This is why the vast majority of grinders made by reputable companies and advertised as "for espresso" tend to start in the several hundreds of dollars range. There's unfortunately no way to shortcut this requirement; loose tolerances would result in too many units being returned when burrs lock up from touching or people complaining that the grind isn't consistent enough. You might sometimes get decent results from cheap grinders, but cheaper grinders will lack consistency and may not be able to achieve very fine grinds at all with some beans.

Unfortunately the cheapest grinder I would recommend for espresso is the Eureka Mignon Filtro, which is generally priced in the US at $210. Also, the vast majority of grinders that grind well for espresso cannot grind well at coarser grind settings, so you'll likely want a separate grinder if you use other brew methods. Your Melitta should be ok for Aeropress, drip, and maybe French Press (not sure at that level of coarseness), so it's not a waste.

Regarding coffee tasting better a day after grinding, this might have to do with the coffee itself. Roasted coffee retains some natural gasses that are created when the coffee is roasted. These gasses slowly seep out as the coffee "rests" after roasting. When coffee is left as whole bean, this process can take quite a long time due to the small surface area of exposed bean. After grinding, the process is expedited a lot as a result of (much) more bean surface area being exposed. If you're sensitive to the flavors of these gasses or if you're buying freshly roasted coffee, this degassing process might explain the flavor difference. This would also explain why water seems to run right through the beans on the first day but not on the second: the gasses are highly soluble in water. The "fast flow" problem is frequently observed among coffee roasters when the coffee is too fresh.