The timer switch in the sauna heater broke replace smart?

[groetschel]

Hello DIYers
I need some help reading the attached diagram.
The "Timer (60 minutes)" broke and I need to replace it.

First, for my theoretical understanding: the voltage between L1 and L2 is 240VAC. How is the timer able to connect to L1 and L2, while only one line goes into the Thermostat?

Second, do you know a smart device that can replace the "Timer (60 minutes)"? I read several articles, which mentioned it is the law that there must be a timer of max 60 minutes. But a smart device could easily handle the 60 minutes max.

Thanks for any advice.
Regards,
Gunnar