Democratic Republic of the Congo is about 12 times bigger than Senegal.

Senegal is approximately 196,722 sq km, while Democratic Republic of the Congo is approximately 2,344,858 sq km, making Democratic Republic of the Congo 1,092% larger than Senegal. Meanwhile, the population of Senegal is ~17.9 million people (90.5 million more people live in Democratic Republic of the Congo).
Tip: This to-scale comparison of Senegal vs. Democratic Republic of the Congo uses the Mercator projection, which distorts the size of regions near the poles.