Translation:He opens the doors of the church on Sundays.
preĝi (“to pray”) + -ejo (“place”)
"Preĝejo" - house of worship, place of worship (of any religion) (in this case this noun may be modified by an adjective indicating of what religion it is)
Synonyms: templo, kapelo, katedralo, kirko, kirkego, moskeo, sinagogo
The church could have more than one door, therefore Sunday as well as Sundays should be an acceptable English translation.