You should ask less interesting questions, then you will get an answer quicker. The first thing to note is, that there were almost no maps in antiquity and certainly no good ones, and there was also no good way to gain reliable information from far away places. Therefore the further information travels the more fantastical it gets.
First of all, Egypt had of course interactions with the Nubian Kingdom to the south, and Herodotus tells us about the circumnavigation of Africa by Phoenicians (if we want to believe him for a change):
I wonder, then, at those who have mapped out and divided the world into Libya, Asia, and Europe; for the difference between them is great, seeing that in length Europe stretches along both the others together, and it appears to me to be beyond all comparison broader. For Libya shows clearly that it is encompassed by sea, save only where it borders on Asia; and this was proved first (as far as we know) by Necos king of Egypt. He, when he had made an end of digging the canal which leads from the Nile to the Arabian Gulf, sent Phoenicians in ships, charging them to sail on their return voyage past the Pillars of Heracles till they should come into the northern sea and so to Egypt. So the Phoenicians set out from the Red Sea and sailed the southern sea; whenever autumn came they would put in and sow the land, to whatever part of Libya they might come, and there await the harvest; then, having gathered in the crop, they sailed on, so that after two years had passed, it was in the third that they rounded the Pillars of Heracles and came to Egypt. There they said (what some may believe, though I do not) that in sailing round Libya they had the sun on their right hand.
Note, that the detail with the sun on the right hand side is correct if they sailed around Africa, however no other source appears to talk about those adventures.
For west Africa specifically, there is the periplus of Hanno. Hanno was a phoenician sailor, who sailed past the pillars of Hercules (The strait of Gibraltar) and then southward along the African coast. However, here we encounter another problem, it is hard to match his description to the geography, and therefore it is not entirely certain how far south he sailed, with some scholars suggesting he ventured as far as mount Cameroon, while the archeological record does not at all support anything like that.
There is also a mention of crossing the Sahara in Herodotus (2.32), where he notes that
[6] After this, they travelled over the desert, towards the west, and crossed a wide sandy region, until after many days they saw trees growing in a plain; when they came to these and were picking the fruit of the trees, they were met by little men of less than common stature, who took them and led them away. The Nasamonians did not know these men's language nor did the escort know the language of the Nasamonians. [7] The men led them across great marshes, after crossing which they came to a city where all the people were of a stature like that of the guides, and black. A great river ran past this city, from the west towards the rising sun; crocodiles could be seen in it.
So people in Antiquity were aware that there is something south of the Sahara desert, but no details, certainly nothing like about other contemporary empires like the Persians, and I suspect that most people then knew that the information is not too reliable, and therefore they probably did not really believe it.