QGIS (merging, dissolve, union) lines of same name

I have street data where roads are segmented for no particular reason. I want to merge, dissolve or union whatever seems fit to make a single flat line. I H
have tried above processes in QGIS but every time I start edit in QGIS and start deleting the vertexes of that line the vertex jumps around as if that line is still segmented. I have attached one image where you can see how a dissolved line when edited its vertex are not deleted in straight path rather its jumps around.

So the questions is how can I make a single, straight, flat line out of segmented based on road names.