There is a very big misconception here in Korea, about the importance of pronunciation when it comes to speaking in English. Many people think that pronunciation is far more important than intonation, yet nothing could be further from the truth.
As a native English speaker living in Korea I find that many so called ‘good’ English speakers have an incredibly boring way of speaking, yet their pronunciation is very good. The reason for this is because the speaker has spent many hour practicing pronunciation and yet spent no time at all practicing their intonation. In many ways they sound like they are reading.
The English language has so many people from so many regions and countries speaking it, that pronunciation has lost much of its importance in recent years. Ask an American to say “aluminium” and they will say “Aluminum”, in just that word you have an almost completely different sound to the way someone from the United Kingdom would say it. Yet both people are speaking English. Other words such as “vitamin”, “tomato” and “water” have very different pronunciations between British and American English and quite simply we do not care.
As a presenter, your job is to make sure that your words are spoken in an interesting way. If you speak slowly, with varied intonation then you are 95% of the way there, even if your pronunciation is not perfect. However, if you speak fast, with a monotonous tone you are going to quickly bore your audience to death and nobody is going to give a damn about your ‘perfect’ pronunciation.
Who cares if you say “professor” with a ‘p’ sound instead of an ‘f’ sound? Personally, I quite like the ‘p’ sound – it gives your pronunciation a little character and uniqueness that is often missing from native English speakers. And I would beg all Korean people to continue to say “perrari” instead of “Ferrari” – to me that sounds absolutely wonderful and always makes me smile. And, hey! If you audience are smiling you must be doing something right (as apposed to snoring – when you must be doing something wrong)
So stop worrying too much about your pronunciation. Speak slowly and clearly and vary your intonation, that way you will make your presentations and your conversations much more interesting to listen to and when you achieve that, your audience are going to pay much more attention to you and the words you are speaking.