Hyperemia is commonly used for arteries and mean “high blood flow within the artery” while congestion is commonly used for veins and mean “high blood flow in veins”
Hyperemia is defined well but the definition of congestion has a little mistake
Congestion is the collection of blood in the tissues but because of obstruction in blood supply. And hyperemia is the same what you said but In hyperemia the oxygenated blood is collecting in the tissues whereas in congestion deoxygenated blood is collecting in the tissues. Hyperemia is mostly physiological although congestion is mostly pathological.