洗手间在哪里？

洗手间 - Bathroom [literally wash-hand-room]

在 - (is) at [many usages but here it means is]

哪里 - where? [a where-question pronoun together with a character meaning inside]

All of these are words contained within the first or second official level of Chinese for foreigners (the HSK exam), and building a basic sentence is actually quite easy :)

It can be daunting to start learning Mandarin because of the characters and tones, but the total disparity from English makes it fun to explore - a whole different world of language!