Is there a way to save my history? A few thousand websites, never deleting my history, because I never know which site I want/need to go back to, and it seems that this may slow down/ hangs pages that are already in the history (note this is not for bookmarks ^o^), and the inbuilt manager only manages to backup bookmarks, which I stopped using 4 years ago...
You can open the combined Bookmarks and History manager via "Bookmarks > Show All Bookmarks" or "History > Show All History".
Then you can select history items with the mouse or keyboard (use the Shift key and cursor Down) in the pane at the right and copy them to the clipboard via the right-click context menu (Copy).
Do not copy an history folder because that will create a smart folder that is linked to the history and not real bookmark items.
You can create a new Bookmarks folder in the Bookmarks Menu folder and paste the items that you've stored on the clipboard in that folder via the right-click context menu (Paste).
You can export the Bookmarks to an HTML file to have a backup.