Are there any restrictions w.r.t. law and copyright to put this translation in BGG file storage, so it will be available to everybody? I really need this information because I would like to do more translations.
Yes. What you have done is a violation of copyright if it was done without the permission of the copyright holder.
"A translation is a derivative work, and only the copyright owner can authorize a translation that will be distributed. ... Derivative works are infringing if they are not created with the permission of the copyright holder. ... Posting something on the Internet is the equivalent of publishing the work. Absent permission from the owner of the copyright in the article, posting is infringement."
Whether or not anyone objects is another matter entirely. Like the others say, ask.