If you can's sing with conviction, is there any point in singing the song at all? I have found that when a line does not make sense, I can alter the words to something which ,to me, fits the spirit of the song, and then can sing it happily. It might be an Americanism which does not translate into English, or possibly a garbled original recording.
As an example, there were some interseting discussions in a recent thread about lyrics sung by Uncle Dave Macon See this Thread . If you listen to his singing, it is sometimes impossible to decipher some of the words. Do we then totally ignore his works, or do we attempt to guess whet the words might have been, based upon the context of the rest of the song, and also any other information about his place in time, the society he lived in and its prevailing political views.
Sing what suits you best. Even songwriters alter their lyrics and sing them incorrectly on recorings.