Most likely the laptop is still being managed by your former employer. If that is the case, then you do not control the laptop and the former employer can still make unexpected changes remotely including completely locking the laptop or erasing it at any time.
If this laptop is not being managed by your former employer, then you should perform a clean install of macOS by first erasing the disk followed by reinstalling macOS & restoring only the data files from a backup made prior to erasing the disk. Do not migrate any apps or settings from the backup since they are likely configured for the former employer. Download & install all third party apps yourself by getting their most recent versions so that they are under your purchase history and "ownership" such as you an own any software these days.
Here is what the previous owner should have done prior to selling or getting rid of the Mac:
What to do before you sell, give away, trade in, or recycle your Mac - Apple Support
Yes, you may have been using the laptop previously, but it was owned, configured, and controlled by the former owner/employer. You should still do all the steps listed in that Apple article (or have the former employer assist you with steps 1-5).
Edit: Another reason for the clean install is that Microsoft has different licensing schemes for their apps and your former employer may have had a special license & configuration of the MS software. Just purchasing your own license may not be sufficient to make things work properly....some things may work, while you may find other things have issues. The easiest way to make sure things go smoothly is by a clean install and downloading & installing new copies of the third party apps.
