That would (as always) depend on the current state of your English skills, your goals, your leaning style, etc. Also, we would need to know the purpose and length of your planned stay in the USA to optimize your study plan. Unless you just want a generic answer….

Communicate with native speakers! That's a quick way to improve your oral English.

(1) Get a language exchange partner. (2) Watch Easy English on youtube: https://www.youtube.com/watch?v=AmlF6xq2SaQ&list=PLlzTQOjV_2alJBgD4GI8LfSbgftXFxrXs. I believe the American edition starts with episode 11. (3) LinguaMarina: https://www.youtube.com/watch?v=MiebCHmiszs&list=PLoDjs_CkjI65GIuJm9Q-GYo69x-uAh5K5&index=1

Try your best to be friendly and polite. Also, try to join a group. Universities tend to have a lot of student groups.

Hello, Furkan! If you want an TEFL certified English teacher to practice having conversations with, I would be happy to work with you! I currently have some openings in my schedule. Let me know if you are interested! https://teach.italki.com/teacher/5129645