You asked
Is the panasonic lumix s 35mm f 1 8 good in low light?
Here is what the site says about that.
From Panasonic Lumix S 35mm f/1.8: Panasonic Lumix S 35mm f/1.8: A prime lens by Panasonic for Full frame cameras, 35mm f/1.8. Specs - Maker: Panasonic - Focal length: 35mm (prime) - Maximum aperture: f/1.8 - Made for: Full frame sensors - Mounts: L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (L-Mount): as marked, 35mm. - On APS-C (L-Mount): like 52mm on full frame; f/1.8 gives about the depth of field of f/2.7 there. ...
From Panasonic Lumix GH5S: Panasonic Lumix GH5S: A mirrorless camera by Panasonic with a 10.2-megapixel Micro Four Thirds sensor, announced in 2018. A low-light video body with a 10-megapixel sensor and no stabilisation.
Quoted from this site's pages.