German (as well as French) is mostly 1 : n. There is typically only one possible pronunciation for a written word (exceptions exist). But for a spoken word there can be several spellings. You need to learn which one is correct.

English is n:m, everything is possible and you just need to learn it.

Finnish is >99% 1:1. A native speaker can should be able to write each word correctly. In practice spelling errors do exist. Partly because in colloquial speach / dialects not all words are pronounced fully according to the rules. Partly because some people are just unable to apply the rules. Not being able to pronounce a written word seems mostly impossible.

However, foreigners should not think Finnish is easy for that reason. There are many sounds foreigners cannot pronounce correctly. And several pairs of sounds that foreigners' ears cannot distinguish.