Complex sentence: However, Grigiškės is not considered part of Vilnius, only of the municipality; that is because joining it with Vilnius, would require renaming many streets in both cities, and it would be too costly at this time.
Split into simpler sentences: However, Grigiškės is not considered part of Vilnius, only of the municipality. That is because joining it with Vilnius, would require renaming many streets in both cities, and it would be too costly at this time.