I don't know which chapter exactly it starts but it's the arc of super fight tournament. The author (manga one) is doing a filler arc so he won't caught up with the webcomic which is after the fight of Saitama vs Tatsumaki.
The anime will adapt that plus Saitama vs Garou. I wish they end it with Saitama vs Tatsumaki, that'd be great. If you want more information about this, try asking it on reddit. They should know more about this subject.
So you mean it will be longer than the first season? Because of fillers? Sounds great in the end.