Welcome to Codewars!

1. Check variable names - carrer should be career
2. You don't need to use the this reserved keyword (remove it) since the variable you created is inside the function and you are not making a class or prototype - no arguments will be called aslong it. this is only used when refering to class instances (see here), so if you're a beginner, I wouldn't get into straight away.

Your code always returns "Full-Stack Developer" since that is the default case as it's an else statement. this.career doesn't exist and will return "undefined". "Undefined" is not less than 0.32 and is not less than 0.65, so it will default to the else statement (this being "Full-Stack Developer").

Hope I helped, feel free to ask if you have anymore queries.