I bought the Witcher 1 game on GOG.com on.
The Witcher 2 bought on STEAM.
I can spend my character in the second part?
Is important the continuation of my character? Involves some extras? Sticking with my stuff?

I think you can. You may have to copy your WItcher 1 save into a new location to get your Steam version of Witcher 2 to see it, but you might not. Not sure.

Importing your save will give you some starting items, but they're not that powerful, and honestly it doesn't make that much sense with the story for you to have them. So it's not a huge deal if you don't import. There are also a few references to decisions you made in the first game, though.

Also, when I played Witcher 2 it was before they released the Enhanced Edition. There may be more benefits to importing your save with the Enhanced edition.

It says the STEAM version of The Witcher 2, The Witcher 1 save that can not be found. It sucks enough. I have not finished the first part, but a lot of time ... I do not want to buy it again on Steam in the first part and start again only to be transferred to the backup. I do not understand why the problem is that I did not buy it on Steam is the first part. Can not be solved somehow? I would like to fully exploit the possibilities offered by the game :)

Put your TW1 save in the folder that has your TW2 saves. TW2 will find it there. I don't use Steam, so somebody else will have to point you to the TW2 save folder on a Steam edition.

Remember that your TW1 save has to be from the end of the Epilogue (Ice Plains or Order headquarters). If you have not finished TW1, you cannot import your save yet.

As far as I'm aware, Steam Witcher 1 and Witcher 2 both use the same save directories as non-Steam. Which should be: C:\\Users\<username>\Documents\<Witcher v#>