XML with Linq - how to save and load those files?! [Unity3D]

Recently I was fighting with saving and loading XML files using Linq which was quite odd.. Especially when this make you headache..

Some of you may not even think about it when you have some small projects but in bigger one.. Data serialization might be real challenge. I was doing some research for dealing with it and I found 2 most common methods: 

• Unity Serialization, which work automatic with just adding [SerializeField] over variable or class
• Writing own serializer and save data to XML, JSON or any other file

First I was thinking that the first method might be good for me but suddenly... Wild "I'm not this type of guy" appear.. And that mean that I have to know what's going on in project so I start digging and looking for information about dealing with XMLs... :P