Upvote:2
They will ask you for your itinerary when you land. If you tell them the truth, they may refuse entry and ban you for breaching the "main destination rule." If you lie and they find out, they will refuse entry and ban you.
However, many people do what you plan to do without getting caught. You need to decide whether or not it's worth the risk.
Upvote:7
In the situation you describe, you could be suspected of lying to get a visa from Finland and not from Germany.