My Mac book has a flashing ? What can I do. Have I lost any data

You can first try restarting the Mac in the Recovery Mode. Hold down the Command + R keys at startup. This will enable you to run Disk Utility, which may fix the problem. If it does not, then restart in the Internet Recovery Mode and press the Command + Option + R keys at startup. This will enable you to reinstall the computer's operating system. You should know that it will install the computer's original OS. If you are running a later version, you will then have to reinstall that version. It can be found in the Apple App store. Good luck.

Your Mac is apparently unable to either find or open its operating system. You may have to reinstall it. Your data and files should still be on the disk. (Do you have everything backed up?) Reinstalling the OS will not overwrite any of your files.

Follow the instructions in the Related Article above. Whether you've lost your data depends on the specific cause of the issue.

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So CMD+r did nothing?

Are you using a Wifi Keyboard?

If so try a cheap PC USB wired KB... Win key + r key.

With all due respect, the " am not winning" does not help us to understand what is happening. Please tell us precisely what you have done or not done. That will help you to help us.