change file table file stream data folder faces error The container can not be dropped
As the message suggests, you need to backup the transaction log in order to move on to the next step. You can do this inside SSMS with a couple of clicks or, if you prefer writing SQL, you can do this:
BACKUP LOG MyDatabase  
   TO MyDatabase_TXN_log1;  
GO

Once this is completed the requisite ALTER DATABASE statements can be run before restarting the SQL Server instance