Grafitti is 'an' (dlaczego 'an'?) very old art form. People have different opinions 'to' ABOUT graffiti. I think, that 'these art' (nie, 'these' odnosi sie do l. mn. a 'art' tutaj jest l. poj) isn`t vandalism.
Firstly I consider, that graffiti is (cos brak) art such as music, films, paintings. If we want to watch (cos brak) film, we go to (cos brak) cinema. If we want 'listening' TO LISTEN to music we must go to (cos brak) Philharmonic. If we want to 'watch' SEE graffiti we 'musn`t' DO NOT HAVE TO go to (cos brak) galerie. We can admire graffiti if we go out ONto (cos brak) street. Graffiti is free and we don`t pay to 'wach' SEE 'them' IT.
Secondly, in my opinion graffiti is entertainment for young people. They don`t watch 'all days TV' (zla kol slow) and don`t commit crimes, but create art. They 'unvold'(ortog, ale nie wiem co chcesz napisac).
Abandoned buildings by 'dint' (zle slowo) of graffiti are attractive. Old places are 'colorfull' (colourful in BrE) and funny.
To summarize I think that people will 'understood' (zly czas, teraz.) that graffiti isn`t vandalism. I believe, that graffiti 'won't limited, but will art' (tego nie rozumiem)