Complex sentence: He was a firm believer of the Puerto Rican independence movement, and once visited Luis A. Ferré, the pro-statehood Governor of Puerto Rico, at the governors mansion and asked him to proclaim the independence of Puerto Rico.
Split into simpler sentences: He was a firm believer of the Puerto Rican independence movement. He once visited the Luis A. Ferré, the pro-statehood Governor of Puerto Rico, at the governors mansion and asked him to proclaim the independence of Puerto Rico.