>>18965122try building somewhere else and face tougher enemies. i just started playing kenshi barely 20 hours in, currently grinding money and exp in Mongrel. its scary at first seeing those 30+ packs of hivers roaming but with the mongrel guards help it makes for easy combat exp.
About your colosseum, how'd did you capture and keep the larger animals? im imagining a "pen" made with walls and a gate