Your description of your problem is not useful as it does not contain specific enough descriptions or copies of the files.
Adding new races is one of the more challenging tasks even if you aren't putting it in a mod yourself. There have been the occasional mod that have tried to add a new race, but most fell apart before they shared anything. I've heard that Aric's mod was planning to add new races, but I haven't looked into their method yet.
You will need to be decently familiar with gdscript to understand the syntax that you must adhere to. If you are not familiar with programming, then I recommend using online interactive tutorials for Python to learn the basics as it is a very similar language. You will also want to use the Debug mod, as it provides more feedback than simply crashing when things go wrong. Even if you did everything else right, you can easily get problems by using a simple editor like Windows Notepad or using spaces instead of tabs.
races.gd is the core file for races, but the critical code that uses it is constructor.gd. If your race uses any attributes besides existing ones, then you will need to change description.gd. If you want your race to be found while exploring then you need to edit explorationregions.gd. If you want to add a racial ability, then you will need to track down the file relevant what you want to change.
NOTE: if you are editing files directly and you Apply or Reset your mods, then it will erase all of your changes. Either make backups of your changed files, use the mod system to apply your changes, or do your work on files that are not in a program file.