Wierd SD card issue

[Enyxiel]

I have a 16 gb Sandisk sd card in a samsung galaxy s7 not rooted. Im having an issue where, upon deleting anything from my sd card it doesnt acrually free up any space. Using an app called diskusage it shows space being taken up by system which is always equal to whatever was deleted. If i restart the phone, using diskusage again shows space being taken up by lost.dir instead of system but once again equal in size to whatever was deleted. If i then delete the lost.dir and restart once more i finally have the space freed up. At the moment im downloading and deleting items on a daily basis so its becoming quite the annoyance having to repeat that process. I've tried reformating several times to no avail.