You can rent bikes in Kungsbacka city centre at Hotel Halland, just by the train station (Kungsbacka station)

https://www.hotellhalland.se/hyr-din-cykel-hos-oss.aspx

Bike map:
https://www.kungsbacka.se/globalassets/gator-trafik-och-utemiljo/dokument/cykla/cykelkarta-kba-a3-2019_webb.pdf

More information about cycle routes in Halland (sorry, in Swedish)
https://www.visithalland.com/upplevelser/hiking-biking/editor_tip/cykla-i-halland