its a virus,
open up command prompt and type tasklist, find the virus then use the taskkill command with /pid then the processname
https://www.microsof*****m/resources/d.../taskkill.mspx
thats how to use taskkill if you dont know how
so as a repeat
1. Open command prompt, go to Run>type CMD>press enter
2.Type tasklist>look for the process that seems to be the virus
3.Use taskkill to close the virus
4. see if you regained your task manager
But i suggest do a full system scan first, or after your choice, but the culprit is prolly a frikken virus