Sync to rekordbox has lost my library

Hi there, I have just used lexicon for the first time and tried playing with a folder on my rekordbox - then I went to sync and I pressed full and now I have lost all 50k and replaced it 154 tracks I was reviewing - can I reserve this ??

Check out Backups and how to restore them

Be sure to only run Sync when you want your RB library to be the same as Lexicon. That’s why you start with a full import

I have found the master.db file - do I copy it and paste it where ?
You mention replace in the rekordbox folder but which one actual folder and where do I find it and how do I get ret it to run again ?
basically I am struggling with the part that quotes
“replace the master.db file in the rekordbox folder.”

Above the folder where you found the backup zip file, it is a folder called rekordbox. Inside there is a file called master.db, that is your current RB database and if you replace that with the one from the zip file, you will restore the backup.

Basically RB cannot restore using your master db file which Lexicon created - as it does not contain any of content that RB needs to restore my library

You don’t need to do anything inside RB, all you have to do is replace the master.db file and then it is done.