I remember having this problem some years ago when I started playing this,now I want to restart it and for the life of me I can't remember how I fixed it then.

nevermind I fixed it :P

No, but you get some useful items that you've gathered in TW1: Armor, silver sword, steel sword.

Yes, when you select "New Game", you then select "Import Witcher 1 Save"
If your Witcher 1 Autosave from late in the game is still in the default location, it, or they will show up.
As for following through, not really anything that changes the game.
If you romanced Shani in Witcher 1, you just get a codex entry to explain why you are now sleeping with Triss.
If you saved Adda, Radovid will mention her, but it will have no effect on the gameplay.
You do get to start with slightly better gear, and a little more money, if you had Ravens armor and the best swords in Witcher 1 though.