A family of Microsoft word processing software products for creating web, email, and print documents.
Sorry to hear that you are having trouble with this situation. Please first check if this happens with all Word documents or only with one specific file. If it only happens with one file, go to File > Info and check whether the document is opened in Protected View.
If it happens with every document, please try opening Word in Safe Mode. Press Windows + R, type:
winword /safe
and press Enter. Then open a document and check if you can select and edit text.
If Safe Mode does not help, please repair Office from Settings > Apps > Installed apps > Microsoft 365/Office > Modify > Quick Repair. If Quick Repair does not fix it, try Online Repair.