I've used this method for extracting the Java and XML files from the apk file but my Java files have a lot of modifications which for sure wasn't there in the original code.
For example, in one class appears for several times access$902, access$902 ,string of digits like 2130903064. They appear in the place of other methods or variables and the project doesn't build because of them.
Can be there extracted the original files or is a solution for this problem? Thanks
No.
Because build process generate .class files, and reverse engineering nevers get to the original code (AFAIK).
If the .apk file was generated using the proguard, this will be less readable and more difficult to understand.
The best alternative is use the AndroChef java decompiler, that runs in windows. This tool can allow you to change the method / variable / class names to be more readable, including the generated files.
The original code only the developer / company owns. I hope you are not using this for something illegal.