Pieces of code or how to do it?

Question

css

Please tell me, I'm making a website and I want to somehow make it up, but I don't know how to approach it. The question is, I highlighted 4 icons with a blue square, is it possible to somehow make a blue line that will go in the middle between them, if so, how?
The second question is, as I understand these lines that are around the heading, this is the "hr" tag, how to make it the same? (more saturated towards the center and almost invisible at the beginning? Do you need to play with the gradient? they didn’t move out, they always turn out either on top of the header, or below...
If you did something like this, maybe you have a piece of code for consideration or tell me where you can read about it, thanks in advance.