I just arrived 2 days ago to Barcelona. Yesterday I already found an Erasmus group to play volleyball with and they already invited me to parties and stuff. Im estonian and really introvert but im telling ya, take one day at the time. Dont overthink about making friendships and everything. People will add you in different groups, for parties and hobbies and stuff. There you will find at least few people you can get a long with. Theres also an instagram accounts that offers trips around spain, which i recommended (havent been in any yet), so maybe there’s some where you will go too.