Hi partner,
1.If you mean you want to delete some columns of the record like "company", "telephone", you could use "Excel Online" to edit the record.
Find "Open in Excel Online" under "EXPORT TO EXCEL" at the top of entity view.

After opening Excel Online ,you could see this page. Right-click the column you want to delete data and choose "clear contents"(The column still exists but the data has been deleted) or "delete column"(Columns are deleted but the data is still there).

2.If you want to delete records, I recommend to use "Bulk record deletion" since you said that the records have flags to determine whether to delete or not.
Go to Settings->Data Management->Bulk Record Deletion and click "New".

You could add filters here and create a delete job.
Hope it helps.
Best Regards
Leo