my database log file size is 20.4 GB from last 2 week

See more:

SQL-Server

my database log file size is 20.4 GB from last 2 week.it is not increasing .i shrink the log file mean query execution is taking half hour .i try remove the log file then also query execution is very slow.50 employees are using my application in the intranet network and accessing the sql server.after shrink the log file sql server is not working properly if i restore the database mean it is working fine .i shrink the log file by changing the recovery model to simple.please tell me how to shrink the log file without effecting the query execution time.why query execution time is more when i shrink the log file.

Recovery Model:full
Auto update Statistics:True

Database Initial size :-161065MB. Around 160 GB but my data is around 11GB it is suddenly increasing dont know what happened.i didn't do any bulk operation.
Database log initial size :-20,967MB. from two week the log file size is fixed.it is not increasing .