Search engine optimisation sounds like something that needs a specialist and a budget. For a local church or foundation it mostly comes down to three unglamorous things.
Your Google listing does more work than your website
The panel that appears beside the search results, with your address, opening times and photographs, is a separate thing from your website. It is free, you can claim it yourself, and for many organisations it is where most people actually get their information. If the opening times there are wrong, it does not matter how good the website is.
Say where you are, in words
Websites often avoid naming the neighbourhood, as though everybody already knows. Write it plainly: the street, the district, the city. Someone new to Groningen searching for a church in Selwerd needs those words to exist somewhere on the page.
One page per thing
A single page called Information, holding service times, the address, the newsletter and the history of the building, cannot rank for any of them. Give each subject its own page with a heading that matches what a person would type.
None of this is technical, and none of it needs to be paid for. It just needs somebody to sit down and do it.