One weekend day a month will not achieve satisfactory progress
Most ad initio pilots need one aerotow launch per year of their age to achieve solo standard, it's unlikely to be less and could be much more. Winch launching will be more launches especially it launch height is low or in poor weather, 2 or 3 flights a month with different instructors will make frustrating progress
The quickest way to get solo is pick a club that does week long courses with Winch and Aerotow run by a good instructor, a 40 yr old should get to solo within 2 weeks and I would recommend that any new pilot get at least some intensive training to avoid frustration.
Once solo has been achieved the mix of check flights and solo to build experience begins and if you are wise never ends, even experienced pilots with hundreds of hours should fly with a good instructor at least once a year, the learning never stops!.