how to fix a block in a location?
Your theme doesn't support RTL layout.

You need to either RTLize (flip) the CSS of your theme or replacing to a theme that does support RTL.

BT 3.0 doesn't support RTL (though there are plans to make BT 4.0 RTL supportive).

A good Drupal base theme that does support is AdavptiveTheme 8, which is also lighter in code amount.