1. To mix up one or more separate things so that you think one of them is actually another one. English = confuse. Idiomatic English = mix up.
2. To be unable to think of something clearly or to understand it because it does not have any order or pattern. English = (be) confused. Idiomatic English = (be) mixed up.
3. To make it difficult for someone to know exactly what to do or what to think. English = confuse.