The provision
The Author offers the Publisher an option to acquire the publishing rights under the condition of this Agreement of other works by the Author considered suitable for German publication.
is, unfortunately, fatally ambiguous because "other works by the Author considered suitable" can be read (by a properly motivated lawyer) as meaning either "other works that the author considers suitable" or "other works written by the author that the publisher considers suitable."
Having said that, it seems to me rather obvious that the intention of the provision was to say this:
The Author offers the Publisher an option to acquire the publishing rights under the condition of this Agreement of other works written by the Author and considered by the Publisher to be suitable for German publication.
or, more succinctly, this:
The Author offers the Publisher an option to acquire the publishing rights under the condition of this Agreement of other of the Author's works considered suitable for German publication.
I say this because the alternative interpretation—
The Author offers the Publisher an option to acquire the publishing rights, under the condition of this Agreement, of other works considered by the Author to be suitable for German publication.
—has the problem of seeming to apply to other works by any author, since the second mention of "the Author" in this interpretation arises only in connection with considering other works suitable for German publication, not in connection with "the Author" being the author of them. So if I am "the Author" and I conclude that The Lord of the Rings trilogy is suitable for German publication, this contract (with the original bolded wording interpreted in the second way) would authorize offering the publisher an option to acquire publishing rights to Tolkien's novels on that basis.
This is ultimately no less absurd than interpreting the original wording
The Author offers the Publisher an option to acquire the publishing rights under the condition of this Agreement of other works by the Author considered suitable for German publication.
as if it were making a stipulation not as to "works ... considered suitable for German publication" but as to "the Author considered suitable for German publication." Again, a lawyer could make that argument (for the right consideration), but it's hard to imagine that the person who created the contract might have had that meaning in mind.
So legally there are (at least) three defensible ways to interpret the provision in question; but as a matter of common sense, only the "other works written by the Author and considered by the Publisher to be suitable for German publication" interpretation passes the "would a fair-minded, reasonably intelligent native English speaker be likely to interpret the provision in this way?" test.