If the seller proposes a small credit in exchange for removing the contingency, compare that amount with the full unresolved downside. A token concession can be expensive if it buys away meaningful protection.
Work backwards from your actual ceiling. A 12% reduction puts the opening around €437,000, but that number only makes sense if you have room for a realistic counter without exceeding what the property is worth to you.
Send the offer through the normal channel with financing evidence, preferred...