Is there anything I should do and tips to keep in mind while staying in Seoul for 3 months?

Hello! I am taking an international trade class and planning to stay in Seoul for 3 months for my final internship. During this time, I want to experience various things such as watching LCK games, tasting various Korean foods, attending parties, and meeting new people. I especially need advice on basic etiquette to follow in Korea and clothing. I heard that getting an Alien Registration Card (ACR) is important, whether for visiting a friend in Hong Kong or for a League of Legends account. Lastly, as a Spanish person meeting people in Korea, I am curious about meeting people, especially romantically. Is my approach too direct in Korean culture? I would appreciate any advice or shared experiences related to this!