Hi Alfsabel
My name is Andre Da Costa; an Independent Consultant, Windows Insider MVP and Windows & Devices for IT MVP. I'm here to help you with your problem.
Click Start, type: regedit
Right click regedit
Click Run as administrator
Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
In the right side pane double click DisableTaskMgr. Change the value to 0
Exit the Registry then restart.