For people who are used to Indo-European languages, the biggest shock while learning Chinese will probably be that it's possible for a language to lack articles, plural forms, conjugation, tense, gender and case.

"I'm going to go buy three loaves of bread tomorrow morning at the bakery." -> "I tomorrow morning go bakery buy three loaf bread." The latter has no articles, tense, conjugation or plural forms, yet it's completely understandable.

Even if you learn all sorts of Indo-European languages, you'll still have a lot of assumptions about what sort of grammar a language should have that are not actually universal. Indo-European languages are quite grammatically complex.