Hello, @Sugus0769, my recommendation is to try to check different configuration settings in your Microsoft Defender Antivirus Policies.
Sometimes you have to adjust less strict rules or notification settings. More information is here. Another thing you can try is to use some third-party antivirus to clean/repair the machine if it is not too late.
One more suggestion from my side is to invest in Microsoft 365 backup solution before it's too late, to have the possibility to recover when you need it. Find more info here.