I love RPG game, but I really hate it when I realize I miss something and I can't go back

the only reason I don't play The Witcher :/

Backtrack as in going back to areas and finishing up other sidequests in previous acts, then yes.

Backtrack as in trying to ask for a quest after turning down the quest, annoying the person, or even failing to offer to help with the quest by changing the subject and asking a different question in a few specific instances, then no.

I also had companions Jacques being killed by bandits before he could talk to me for the first time and Nicolas being killed by me when he aggroed me before his superior told his men to stop attacking me and offer Nicolas's services to me. In this case, raise dead spells do not work at all on them since they have not agreed to join you as companions yet.

Fortunately in this game, it is usually possible to use console commands to open a quest, to spawn any character in the game to appear next to you and behave as if they are speaking to you for the first time, or to spawn a required quest item into your inventory if you missed something. This option helps to make it less likely that you will end up at a dead-end in this game and sometimes might save you many hours to restore to a previous save game.

sounds cool

thanks for the answer :D