# we

This refers to Paul and Apollos but not the Corinthian church. 

# God's fellow workers

Paul considers himself and Apollos as working together.

# You are God's garden

"You are like a garden that belongs to God" or "You are like a garden that God makes grow" 

# God's building

"and you are like a building that belongs to God" or "and you are like a building that God is constructing"