Topic sentences have a dual purpose to:

Topic sentences have a dual purpose to  communicate the purpose of the paragraph and relate the paragraph back to the thesis. Or if you talking about something exciting, topic sentences have a dual purpose to communicate the purpose of the paragraph and provide exciting details.

Explanation: Hope this helps:)

kenny´s more than 25 years of relevant public service. in the army for two decades, as official representative for four years, and now for the department of state, as ambassador. this career clearly demonstrates great capacities in the public sector.