Also, I wonder if the security in Spain is really bad? When I went to Argentina for the Spring Festival, I also saw in the travel guide that the security is not good, with many pickpockets, etc. When I got there and lived in a good area, I thought it was very safe and going out at night was no problem ?

The public security is actually good, as long as you pay attention and don't draw too much attention, small thieves generally won't target you. As for going out at night, if you are wandering outside alone at 12 o'clock, even the city center is not safe.

As long as you are more careful than at home. It gets dark very late at night, and there are a lot of people on the streets, all of whom like to eat, drink and chat on the street.