How to remove stuck mode in SQL Server?
You did blunder by restarting SQL Server. You should have not done that.Unless SQL server will recover the database fully and comes to state where database finds itself in same consistent state as it was before the force shutdown it will show in recovery state. Your best bet is to wait and watch you cannot run any transaction on recovering database. Also since you manually killed SQL server process while it was  rolling back a query its even more worse. Now when SQL server database will come online the whole rollback process will start from beginning not from point where you killed SQL server process/query. So it might take time and unless it fully rolls back the previous killed query it won't come online neither you can force it to.

One advantage you can have is if you have Enterprise edition SQL Server will come online after redo phase of recovery. So that might be little relief to you.

PS: Seriously avoid any such random suggesstion given on web. You should take this as a lesson to never kill SQL server process or restart SQL Server if certain query is taking time. You should wait and chec rollback status of query using below script

select session_id,
blocking_session_id,
wait_type,
percent_complete, 
((estimated_completion_time)/1000) as Estimated_Complettion_time_Sec,
((total_elapsed_time)/1000) Toatal_Elapsed_time_Sec 
from sys.dm_exec_requests where status='recovery'