My MacBook flashes the folder with question mark.

You should when booting thru the option key see your recovery drive and your startup drive. Reinstalling your operating system does not delete anything in personal files as it only reinstalls the system. When you were in disk utilities you should be seeing the main drive as well as the startup volume. If not go to the top under view click on show all devices. It should look like this . Except that your may also show the base drive.

Get out of that screen and go back to main recovery screen. Get into disk utilities. Did you use the view in the top menu to show all devises? I would like to see a pic of what disk utilities is showing. And could you tell me what year MacBook Pro you have? And operating system.

OK. Run the repair on the Apple Disk Image. If this does not show a full drive then reboot and hold down Command Option R. This will go to single user. It will look like a windows boot . When it finishes, type in /sbin/fsck -fy and hit return. If it says system was modified do it again . If it says system ok type reboot hit return. See if you can now boot. If not you will have to go to internet recovery. Command Option R. You get a screen with a spinning globe and a progress bar. when connected you may have to put in your internet connection. It will show a recovery screen where you can use disk utilities and recovery. Start with disk utilities again. If you can get it to show a full drive path then you can reinstall. If you choose to erase the drive . you can still reinstall from there. but it will install the operating system that came with your MacBook Pro or the closest available. Which would then mean you would have to update to get back to the one you are running now. Then you can use time machine to return your files. The updates can be found by typing( older Mac OS) in your search bar on your browser. It will give an apple link.

Since you have access to you base volume Start with the option key down and boot to your base volume. Which is recovery. Click on an go to disk utilities and repair the drive. then close out of disk utilities and reinstall your operating system.

If your entire system is backed up on your Time Machine, use that to install your OSX system. If it doesn't work right, reinstall the OSX system (you can do it online at Apple.com or if you have a disc, use that). After the system is working correctly you may want to use your Time Machine to replace any specific files you want on your computer. Good luck!

Sorry to hear that. Did you try Command Option R? You need to find a way to repair your hard drive in order to get an operating system on it. Otherwise you will need to replace the drive and start over. Do you remember what name you gave the startup volume? You could try using terminal in the recovery volume. it would be accessed at the top menu under utilities.https://computers.tutsplus.com/tutorials/how-to-verify-and-repair-a-disk-from-the-os-x-command-line--cms-21561

No drive while in internet recover. Have a 2010 MacBook running High Sierra and Command S works in my computer. If terminal commands will not mount the volume using fsck wont do anything either. And it won't work in terminal. The link I gave you is the only one I know for terminal. fsck only works in single user. Command S would not get you to single user? The only thing I can tell you is I think you drive has failed. You will need to replace it.

Time Machine will not install an operating system you can boot to. It only installs the files and changes made to your operating system. So that if you have a problem on your computer from something recent, you can revert back to a date when it was running well. Since you have Time Machine You could erase your drive. That would be the second drive, per my image. And reinstall you operating system. then use time machine to transfer you files and setting back on.Restore your Mac from a backup - Apple Support

I made a mistake on single user mode it is not Command Option R . It is Command S. Sorry.