Simplify the following text for a Grade 10 native English-speaking person.
Original: Line 9 ( LÃ nia 9 in Catalan ) is the newest line in the Barcelona Metro network , currently under construction , with only five complete stations , all in Santa Coloma de Gramenet .
Simplified: Line 9 ( LÃ nia 9 in Catalan ) will be the longest automatic metro line in Europe . It is the newest line in the Barcelona Metro network , currently under construction , with five stations completed so far , all in Santa Coloma de Gramenet .