Enough with the dinging!
Your Australian teacher was correct that the question should say
"being lost" instead of "losing seriously". In general, the topic
is phrased in a strange way.
I think that both you and your teacher are right in this case. In
fact, you could write an entire essay about how progress has influenced
language and culture. You say that it's just one reason, but then
you go on to list several reasons: the internet, economics, jobs,
foreign companies. These individual factors can be each be used
as a reason. You're right, though, that you could also write
about tourism as a reason.
In regards to your question about your model interview, no, you can't
get a 6.5 on the real test. Only whole band scores are given for
the Speaking Test, so you would get either a 6 or a 7.
As for your final question, yes, it's true that you should have a
logical flow to your speech and reasoning in the interviewer.
Sometimes it's a good idea to list several reasons, as you suggested.
I hope I've answered your questions! Let me know if there is
anything you're still confused about, and I'll try to get back to you
sooner this time.
John