This depends on your current proficiency. Simply being in the country and actively engaging with academic discussion, reading, listening, and learning, your language skills will improve.
It also depends on how long you are able to study abroad. If you only have a summer break, a standalone course is a good starting point.
A semester stay would enable you to enroll on a concurrent program—improving your language alongside gaining academic credit.
If you can commit to an academic or calendar year, you have more scope to consider what would work best for you: Would you prefer to elevate your language proficiency before joining academic classes? Choose the language pathway option. If you’re excited to start academic classes and your language proficiency is very close to advanced, you can consider concurrent programs.