I'm a long way from a Bridge expert, but if I understand your problem correctly, you might want to try shifting between some of the optional "workspaces" and see if you'll get the scroll bars you want.
Under the Window menu, choose Workspace, and then slide over and choose a workspace...such as Preview.
Each of the workspaces rearranges the various panels in Bridge...maybe you just need to find a workspace that works the way you want...and of course you can create your own workspace without too much trouble.
Also...if the icons and other things that appear in a particular panel don't take up enough space, there will be no need for scroll bars, and then the scroll bars will not appear.
I was in the preview panel whatever that is supposed to do I don't know.. it
is the panel below it that has the scroll bar...
NotAlwaysSuite meant you should try an other workspace using the names at
the top of the bridge Window right centre. You can explore those for
different workflows but you can also create a workspace for your own purpose
and save this.
However I think you are talking about the thumbnails in the content window
that are not complete visible and show a horizontal scroll bar.
For some reason you have (accidently) changed the layout from auto to
horizontal. The easiest way to get it back to normal is to go to the
triangle right next to the workspace names and click on this icon. The fly
out menu gives you first of the row the reset workspace option. Click on
this and you should be OK.
Second option is to go the little menu icon top right of the content window
and from this small menu choose auto lay out.