This happens because it is likely that you do not have the spell check correctly set on your computer or it has simply been deconfigured for some strange reason.
Our templates are originally designed in English. If you are using MS Word and your spell checker is in a different language, you are probably marking the words in English as errors. You must change the language of your spell checker. Please check the following information,
Check spelling and grammar in a different language https://support.microsoft.com/en-us/office/check-spelling-and-grammar-in-a-different-language-667ba67a-a202-42fd-8596-edc1fa320e00?ui=en-us&rs=en-us&ad=us#ID0EAABAAA=Office_2007