Questions & Answers about Ele é o namorado com quem vou viajar.
Why is com in the middle of the sentence instead of at the end like in English?
In English, we often end a sentence with a preposition ('travel with'). In Portuguese, this is not allowed. The preposition must come right before the relative pronoun it relates to, so you literally say com quem ('with whom').
Could I use que instead of quem here?
No. When a relative pronoun refers to a person and directly follows a preposition (like com, de, or em), you must use quem. You only use que for a person if there is no preposition involved.
If the sentence was about a girlfriend (a namorada), would quem change to match the feminine gender?
Why does the sentence use vou viajar instead of a single future tense verb?
vou viajar uses the present tense of ir (to go) plus the infinitive verb viajar (to travel). This is the most common way to express the future in everyday Portuguese, working exactly like 'am going to travel' in English.