Hello, after noticing my brake hose had a hole in it I bought a new one, successfully unscrewed the bolt that held the other end but got this one completely rounded.

Now, I was wondering how to go on about this, should I get a saw and just split it and weld it onto a new screw?

 

You don't "weld" a new fitting onto the end of a brake line.

Go look at metal brake lines at the autoparts store to see how they work. You're probably going to have to replace that metal line. And the ones you buy at the auto parts store usually don't fit. They have the wrong type of flare and the threads might be different.

In the meantime you will need penetrant and maybe so heat to attempt to loosen that - but it may be too corroded by this point