Complex sentence: Painting began in late 1979 with a targeted completion date of October 1980 but the work was more complicated and time consuming than expected and in 1982, while still under construction, the uncompleted mural was vandalised with right-wing slogans.
Split into simpler sentences: Painting began in late 1979 with a targeted completion date of October 1980. The work was more complicated and time consuming than expected and in 1982, while still under construction, the uncompleted mural was vandalised with right-wing slogans.