Learn Swedish: Hon tänker mycket på studien. - She thinks a lot about the study.

Tänker is used for the actual action of using your brain to ponder or concentrate on something. Tycker is for expressing a personal opinion, and tror is for believing or guessing. Since she is actively pondering the study, we must use tänker.

Why is the preposition på used here instead of om for 'about'?

While om often translates to 'about', Swedish uses the specific pairing tänker på to mean 'thinking about' or 'having on one's mind'. Verbs often have fixed prepositions they lock onto, and for tänker, it is almost always på.

Is studien the word for 'student' or 'study'?

It means 'the study' (like a research project). The base noun is en studie, and we add -n to make it definite (studien). A student would be en student, and 'the student' is studenten.

Why does mycket come before på studien?

In Swedish, adverbs that describe the verb (like mycket describing how much she thinks) usually come directly after the verb. Putting it at the end of the sentence would sound unnatural.