Which sentence is correct?
I got a presentation on this Friday, so I was doing it last week.
I got a presentation on this Friday, so I was preparing it last week.
Will the word "prepare" relate to collecting data, producing slide and prasticing the presentation?
Is it incorrect to use "doing" in my case?
There are a number of common collocations with "presentation" but "do" is not one of them. Here are some good expressions:
- deliver a presentation
- give a presentation
- prepare (for) a presentation
Although "doing a presentation" is not a good collocation (and so should not be used), native speakers would take it to mean that you are delivering or giving the presentation.
By the way, your sentence contains a few examples of non-standard usage. It would be better to say "I have" or "I have got" rather than "I got". Also, it is not usually correct to use a preposition when using "next", "last" or "this" to modify a time word, so just "this Friday" not "on this Friday".
So, a better sentence would be:
I have (to give) a presentation this Friday, so I was preparing it (all of) last week.
I hope this helps.