Hi pafurijaz,

re:
> Thanks for any suggestion and help to solve this problem

For troubleshooting I'd suggest working with curves as the cutting objects, they will be easier to examine to see problems.

To start with after I squished the base curves down to 2D I just selected them one by one to see if they were closed and this one does not have an object type of "closed crv" so it has a little opening in it somewhere:



Then the other area that could be problematic is this overlap Pilou was mentioning above, I'd get that cleared out from the curves before trying to cut with it:



Another thing to look out for - it's subtle but notice how these edges are darker than the other ones?




It looks like that because there is more than one edge drawing on top of each other there. If you zoom in to those areas you can see a small little surface sliver between larger pieces. Small slivers can be problematic for cutting operations.

- Michael

Thanks Michael for these suggestions, for what you indicate as double curves are a cosmetic necessity and I need to simulate the spaces between the boards on the bridge, they are 8mm of space between the two lines. 
However, I will keep these tips in mind and will try to use these techniques, thanks again.