How to prevent Android from creating Android and Lost.dir folders on external otg storage?
Android folder is used to keep data about your apps. Deleting it from the internal storage or external storage (when used as adoptable storage) will cause the loss your apps' data. 

LOST.DIR is a folder used to place recovered files during boot. It is usually empty. Deleting this folder is safe.

In your case, you can delete both folders without creating any issue. Delete the folders, then disconnect the SD card as mentioned by @Chrisii. It is a process that you will have to accomplish every time because the folders will be re-created by the Android OS when the SD card is connected.

All you need to know about LOST.DIR folder on Android devices

What is the use of an Android folder? What happens if I delete this folder?