Do I erase os base system before I reinstall?

Neither, I would recommend the following before you do something dramatic like doing a re-install which likely is not necessary. We need to see what is installed to see if you installed something that is causing the issue. Without information and then doing an install you may be completely wasting time.

Please navigate to the Mac App Store or navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211

Boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

What is on the startup screen of your Mac when you turn it on, does it look like any other ones in Mac Startup Screens ?

You have not explained what you are attempting to achieve. Mac OS does not need to be reinstalled periodically like MS Windows so we need a more comprehensive question explaining the context of the issue before we can give you an intelligent answer.

What is "this screen", I think you intended to add a photo or a screen shot but you did not. Again, without some information it is tough to help you.

Your welcome?

Very glad to hear!