A finnish person here. Our second language is swedish not norwegian :-). Aside from that, it is true that many signs etc. are written in both finnish and swedish. People working in public sector are also supposed to know swedish.

Outside of few swedish speaking areas you are better off using english as it’s more widely spoken by the general population.

If you want to use a CMS that runs on PHP, take a look at Processwire. It’s flexible, intuitive and (if such things matter) fun to code for.

Downside being that it’s not well known although it’s been around a long time.