словосочетание to be a teacher сделать утвердительным вопросительным отрицательным 
с местоимениями I,he,she,if,you,we,they 

I/you/we/they want to be а teacher или he/she wants to be а teacher
Do you/ they/ we want to be а teacher? или Does she/he want to be а teacher?
I/ you/ we/ they don't want to be а teacher или She/he doen't want to be а teacher