Congo is significantly farther north than Paraguay.
The Democratic Republic of the Congo straddles the equator, with territory extending from approximately 5°N to 13°S latitude. Its capital, Kinshasa, sits at roughly 4°S.
Paraguay lies entirely in the Southern Hemisphere, between approximately 19°S and 27°S latitude. Its capital, Asunción, is at about 25°S—roughly 2,500 km (1,550 miles) south of the equator.
So while Congo has territory in both hemispheres, its northernmost points are thousands of kilometers north of Paraguay's southernmost reaches. The question contains a common misconception: Congo is not exclusively in the Northern Hemisphere, but it extends much farther north than Paraguay.