distorted uv unwrapping

I want to know how I can fix distorted uv map?
I tried different unwrapping ways but still there are some imperfection ?
I attached my file to see the problem.

I want to know how I can fix distorted uv map?
I tried different unwrapping ways but still there are some imperfection ?

Each model is very individual and only practice can help you to see how to unwrap it correctly and also you need to watch some unwrapping tutorials there's a lot of them on youtube. When you will know all basic methods of unwraping you will able to combine them and choose the best way to unwrap your model. Good luck.
I've unwrapped your model as I would do this. I used "Follow Active Quads" method for this.
UV_problem.blend