The fact that they are meaningful German words that appear in a dictionary makes the task no easier, there are many meaningful 5 letter words. It is just like me saying "I have chosen a number, guess what it is?" then later saying "Oh, as a hint it is between 1 and 100000000000000000000000000000000000000000000000000000".

The way I see it is that 97 letters means there must be 2 letters that "overhang" the other columns.

In decrypting the first layer of the cipher we have 5C2 = 10 possible places to put these overhanging letters.

Then after assigning these we have 120 possible permutations of the columns, meaning we have 1200 possibilities for the partially decrypted ciphertext.

Then we must again assign 2 overhanging letters in one of 10 ways and try another 120 possible permutations in order to get the plaintext.

This gives 1200^2 = 1440000 possibilities to try.

I doubt this one is easily done by hand (especially since there is no known method to check whether the partially decrypted ciphertext is correct).