Learning Portuguese might indeed be productive when you want to stay in Lisbon. It will certainly help you relate to the locals and to your new environment.
Portuguese is the sixth most spoken language of the world which has its root to a group of languages called “Romance” or “Neo-Latin” that evolved from the city of Rome, earlier called Latin of Ancient Italy. And that for a time Latin gradually replaced other native languages in the Iberian Peninsula, or as the country of Portugal was founded it went to have adopted it as its national language in its own particular Romance which happened to essentially Portuguese, and today it is only in the region of Spain that the same Romance is spoken.
This takes us further on to the fact that the provincial use of Latin varied in terms of the position each region had with Rome where lexical changes were constantly created by the urban masses need for expression such that, the use of traditional Latin verbs, “comedere” (comer in both Portuguese and Spanish) meaning “to eat”, or the word for cheese (caseus) which is “quejo” in Portuguese and “queso” in Spanish shows the fact that Portuguese and Spanish are most similar than the other Romance speaking regions where the verb “comedere” had the term “manducare” for both Italy and France, or for cheese, the term “fromage” in French and “fromaggio” in Italian.
You should also know that there are other languages that have influenced Portuguese over the years when other groups settled in Portugal which can be traced back earlier to the times of the Celtic like the word “ontem” for “yesterday”, the Scottish Gaelic “esquecer” for “to forget”, the Germanic “”roubar” meaning “to steal” and “guerrear” meaning “to wage war”, and the Moorish with which the “al” prefix like “asalmofada” meaning “pillow” is much introduced in about five hundred words.
Other influences in fewer words though are still to note of like those which had been absorbed into Portuguese like, the Malay jangada (raft), of the Chinese cha (tea), and of a language from the south of France, Provencal, with a word such as “rua” (street) carried through the infiltration of the French manners and customs in Portugal when they went to Portugal as pilgrims, courtiers, statesmen, scholars and soldiers of fortune to help fight the Moors during the tenth and eleventh century.
Actually, these are but the introductory but which are significant to learn about Portuguese. To learn more about how the language can be spoken should require one to go to a school of language in Lisbon, Portugal.