Hi Poyraz,
Sorry no manual for your era machine as mine is from the early 60's, however a forum poster under the name of "Wrench" did produce a DVD many years ago with a lot of Deckel info on it, maybe be worthwhile seeing if its still available.
Based on my machine, behind the bevel gear on the horizontal drive is a tribach arrangement for holding the bearing in, which I presume is for adjusting bearing pre load as there are 3 set screws as well as the 3 hold down screws, also there are shims in there, again for adjusting clearance between the horizontal and vertical head bevel gears. On mine these bevel gears get lubrication from oil flow through the upper bearings in the vertical head, so the earlier comment about grease there would raise a flag. In one of the photos attached you can see the nut and lock washer for holding the bevel gear on.
Yes, its always interesting to see what handiwork others may have done prior to your ownership, also the Deckel factory seems to have incorporated changes during production that were not documented to the outside world. Good luck with the restoration they are a very versatile machine and worth the effort as an attached photo shows, repairing a dough mixer paddle. Alan.