Resolve "Learning materials"

Review here

Closes #276 (closed) #236 (closed)

_data/navigation.yml

@@ -26,7 +26,7 @@ header:
         url: "services/software-overview"
       - title: "Software Engineering Consulting"
         url: "consulting"
-      - title: "Backone Services"
+      - title: "Backbone Services"
         url: "services/backbone-overview"
   - title: "Learning & Training"
     entries:
@@ -90,7 +90,7 @@ header:
         url: "media"
       - title: "Careers"
         url: "job_offers"
-  - title: "Can we help you"
+  - title: "Can we help you?"
     url: "contact"
 
 footer: