I'm wondering if it's possoble to edit/mod Daggerfal? I would like to remake it if possible or at least fix the grammer mistakes, it's a nice game and could be nice to revivie it somehow.

Because of the dynamic way maps are generated in that game, modding it would be difficult. There are some mods for the game, see this page for what is out there. I think some of them even fix the text errors

http://www.uesp.net/wiki/Daggerfall:Files

This is a myth. Aside from the foliage placement and NPC/monster spawns, Daggerfall's content is either static or procedurally generated from static data files. Every player gets the same towns, terrain and dungeons (barring glitches that temporarily rearrange terrain and usually kill you in the process).

Daggerfall is difficult to mod because the data formats were largely undocumented for years, and even though the game is better understood now, there aren't a lot of good tools. There are tools for graphics, text, quests, and terrain/climate. A dungeon/town editor is plausible, but hasn't been created.

I sort of like the grammatical errors. When they occur in dialogue and books it just feels like you're in a world where the NPCs have unreliable educations. There are lots of little text and quest mods, though. You might not need to do any work depending on what you're looking for.