[Blur tool doesnt work?]

Okay so if I were in Krita, I'd solve it by clicking on this lock, to allow me to go past the limit, the borders. 

[Blur tool doesnt work?]

Hello,
 selected the boy in the middle to have him separated from background (and two girls in the front, you know what I mean). I then used filter "Depth of field" but now the edges of two girls look too sharp on some parts. I tried to use soft eraser but soon realized that it'd be transparent. I then wanted to blur the edges with the Blur tool, but it doesnt work, it does nothing.
Any suggestions?
Wish you nice evening and thank you

[Merging objects into one (and keeping original colours and shapes of lines)]

Man thanks! didnt think the answer would be so easy, worked quite well

[Merging objects into one (and keeping original colours and shapes of lines)]

Hey, I have a logo and I need to merge all the shapes.

The paddle is white and over it is the right hand on the person. Below it is rest of the pic.

No the paddle has different line shape than rest of lines.

The rest of logo is all joined and added, but I cat figure out how to add paddle and hande without changing colour or shape.

When I tried to Add in Geometry, it went black.

So my goal is to have the paddle and hand along in one big object, like in here:

I also tried Merge Curves, but the paddle went black and white.

Maybe something like changing the curves (lines) into shapes would help, but I dont know how to keep it in vector.

Thanks

[How to make part of curve white? (when approached by black background)]

Hi and thanks!

so when I use Divide it will be in raster right?

I'd like it to be in vector, so it probably gonna get complicated, but I will manage.

Also, how can I tell right away that its been rasterized? It looks same to me.
 

[How to make part of curve white? (when approached by black background)]

Hi, I need the part of the paddle that is lying on black background (boat) to be visible (=be white). But just that one part. 
I dont want a round end of the curve, thats why I dont want to start a new one. 
How to achieve that?