Lot of log files in $FSLOG generating. How to stop?
Make a backup. Those are not log files - where did you get this idea from?

Yu basically store some data in the file system - MyDatabaseStream_Filegroup_Data\$FSLOG\

Database FIleStream feature. VERY nice if you (a) know what you do there and (b) need it.

Either you back up - thzen surplus can be deleted - or you move it to another disc or.... you disable file stream storage.