Thanks for your answers. Only a five sidequests for the whole game? It's OK, I thought, that I was missing something huge. I didn't meet the Greu's birthday quest, but maybe I wasn't searching enough.
I've got only one more question, the last one - where should I identify my unidentified stuff? I've got a couple of unknown rings and potions and don't know, where to identify them.

Identification is based on your Object Knowledge stat, and happens automatically. As far as I know, there's no other way to do it.

OK. Thank you very much.

Hey there,
has anyone found the note on the wall next to the guy with an eye patch in the tavern?
It's just on his right side.
Well, it speaks of a hermit called Oliver who sort of invites you to a treasure hunt, if you first place an emerald in his chest that is.
I never found that guy nor his chest, don't know were to look either but i'm pretty sure it's yet another sidequest.
Grtz

In addition to those named above, there are also sidequests involving Cooking for Goblins, Lord Inut, and the bank of Arx. It's really quite a few, and you need to really pay attention to what you are doing to get them all done successfully in a single game.
The first step--finding the chest to put the emerald in--is very simple, because you can come across it during normal exploration (and may even have an emerald on hand at the time), but the rest is not nearly so straightforward. This is quite a long and winding quest that takes place in several different areas; you will need patience and a shovel, as well as the ability to work out the various clues. As far as I recall the end reward is put in place at the start of the game, not spawned when you successfully complete the hunt, so there is nothing stopping you from going right to the spot once you know where it is.