all missions like: go to this place find someone, find some item or person somewhere on the map, the truth is that I could never complete any of these missions, I even walked around in the adjacent fields where the target was supposed to be but I never found it , I even followed the clues such as traces etc. but it seems that this is some kind of error

For missing child quests, just type /say follow me! and they will join you, after which you can lead them back. I generally go to all 4 corners of the tile to do it as that always gets it. For outlaw quests, sometimes they don't appear to be there, because they are in stealth. for this you can just use the /search command or s. Although I can't prove it, i'm pretty sure research quests never have hiding monsters, and you just have to be more thorough, as you have to be pretty close to see them.