Passing from train station to airport

Ashraf, you cannot take a train from Hong Kong to Guangzhou under 24 hour visa free transit scheme. You have to be aware that only entering Guangzhou by air, you would be issued the 24 h visa-free transit under qualified travel itinerary. So, please, do not even think to try to do as you have originally planned because you will not be allowed to board the train in Hong Kong.

If you already have a flight ticket from Guangzhou to Egypt, then you have to buy a flight ticket from Hong Kong to Guangzhou, but you have to take care that the time counted from the arrival of your flight to Guangzhou, until the departure of your flight from Guangzhou should not exceed 24 hours even for just a minute!

The alternative to this option is, indeed, to obtain a Chinese transit visa in advance in order to reach Guangzhou by train and then to proceed by your flight to Egypt. Now, you should decide what of the two options would be more convenient in your case.