MacBook Air i7 overheating and slow

This was a real surprise that such an expensive gear can have such a problem from day two. It has only been 8 days and today the fan was going crazy and the simplest tasks took ages to load or never loaded. I restarted, went better but started again and totally unacceptable. I don’t know what to do, I trusted Apple on this, never expected such a basic problem. My daughter cannot believe that this gear is one of most expensive she wants to give it back