Welcome to the Vulcan forum Jarek. I checked the map and find that Warsaw is 8,500 miles due east from Alberta.
I would come join you for a ride, but there is a big pond between us!!
I can`t help you with an owners manual, but here is a link to a free downloadable Kawi VN750 service manual:
Many or most of the rider/owners here bought our Vulcans used and never got an owners manual either. If you really feel the need to have one, check our link to all things vn750 on ebay. One shows up once in a while. There are very few changes from 1985 to 2006 models, so any model year`s owners manual should be pretty much the same.
See my link below, and spend some time reading the Vulcan Verses.
Especially note the MF-AGM battery, NGK-Iridium spark plugs, and the rear spline lube.
One money saving tip is to use constant velocity joint lube for the rear splines. It is available at any auto supply store typically for $5-$10, compared to the Honda Moly60, which is often very high priced ($24 per 100ml tube (3 1/2 ounces) here at the local Honda stealership).
The CV joint lube usually comes in a heavy duty plastic bag, and you will have a lifetime supply. Just cut off a corner to give a small 1/4 inch opening to squeeze out what lube you need, then fold over and seal off for next time. I checked this out again last night with a 2nd mechanic with 25 or 30 years experience, and has been riding bikes for as long or longer, and he agrees that the CV joint lube should be as good as anything available for spline lubes.