Is it possible? Maybe someone can tell me?

You need to use mods. They are very simple to install. Just follow the guidelines here:
https://www.gog.com/news/mod_spotlight_planescape_torment_mods_guide

If you are playing for the first time I would just limit myself to the widescreen mod + UI mode, or add the fixpack. But would leave out unfinished business. Of course you are welcome to play any way you like :)