Some of the most frequent verbs in Portuguese don't follow the regular patterns. You've already met a few of their forms — Eu quero mais um! at the feira, ela vai a pé and ela faz um lanche in Luana's day. Here are three of them in full:

Pronoun	Fazer (to do, to make)	Ir (to go)	Querer (to want)
eu	faço	vou	quero
você / ele / ela	faz	vai	quer
nós	fazemos	vamos	queremos
vocês / eles / elas	fazem	vão	querem

The forms in bold are the irregular ones. Fazer and querer only misbehave in a couple of places: faço takes a ç, and faz and quer lose their final -e. Ir is irregular all the way through — learn it as a little chant: vou, vai, vamos, vão.