Hi there, I can understand your problem very well if your mother tongue is English. If it was Italian or Spanish you would not have any problem with this formal way of addressing someone.
Since my mother tongue is German I add a German explanation from Wikipedia first and will try to find an English one afterwards:
Das Portugiesische hat wie die spanische Sprache eine von einer Possessivkonstruktion abgeleitete Anredeform entwickelt você, das eine Kontraktion von vossa mercê „Euer Gnaden“ darstellt – *você gilt in Portugal und den afrikanischen Ländern portugiesischer Sprache als semi-formell. Informell wird sich mit tu angesprochen, formell mit o senhor/a senhora und dem Verb in der 3. Person Singular
Maybe you understand German and all is clear you you now.
Ok, I found something in English which seems clear enough to me:
Generally speaking, tu is the familiar form of address used with family, friends, and minors. Você indicates distance without deference, and tends to be used between people who are, roughly, social equals. O senhor / a senhora (literally “sir”/“madam”) are the most ceremonious forms of address. English speakers may find the latter construction akin to the parliamentary convention of referring to fellow legislators in the third person (as “my colleague”, “the gentleman”, “the member”, etc.), although the level of formality conveyed by o senhor is not as great. In fact, variants of o senhor and a senhora with more nuanced meanings such as titles as o professor (“professor”), o doutor (“doctor”), o colega (“colleague”) and o pai (“father”) are also employed as personal pronouns. In the plural, there are two main levels of politeness, the informal vocês or vós and the formal os senhores / as senhoras .*
Is this of any help to you.