Hi,

often with modeling i have blue edges that i can’t delete how can i get rid of them?

I got rid of them but not the way i like.
I deleted a lot of faces and rebuilded them.

alt+delete tends to do the trick for me when I need something like that deleted.

press ‘M’ and then use the weld tool and click on every point in contact with your ‘blue line’ (which is an open edge)