Although our job titles are different, our responsibilities overlap quite a lot.

overlap 由前缀 over-（表示"在...之上"）和动词 lap（重叠、包裹）组成，字面意思是"在...之上重叠"，引申为"部分相同或重合"的意思。在这里指工作职责有部分相同或交叉。