There are several options for Turkish language courses in Istanbul, catering to various levels and learning preferences. Here are a few popular choices:

1. Istanbul University Language Center: Offers comprehensive Turkish language courses for foreigners, ranging from beginner to advanced levels. They provide both in-person and online classes.
2. Tomer (Turkish and Foreign Languages Research and Application Center): Affiliated with Ankara University, Tomer has branches in Istanbul and offers well-structured Turkish courses with a focus on practical language skills.
3. Dilmer Language School: A specialized language school in Istanbul that offers a variety of Turkish language programs, including intensive, semi-intensive, and private lessons.
4. Yunus Emre Institute: Known for promoting Turkish culture and language abroad, this institute provides Turkish language courses that include cultural immersion activities.
5. Turkish Language Center (TLC): Offers customized Turkish language classes in Istanbul, designed to meet the needs of different learners, including expats, students, and professionals.

Each course has varying schedules, so it’s good to contact them directly to find the best fit for your needs.