"Explain two phrases to me, please" ("Explain me" = объясните меня! We need "to me" for this phrase.) The first phrase isn't typical way of expressing oneself, but anyway... A bummer is a disappointment. By adding "the" and making it something that we've got, it makes the disappointment sound significant. This is a fairly recent slang grammar form. In the second phrase, a "walk of life" is your life-path or vocation.