How many people did Moses bring out of Egypt? How large was the area of the Promised Land? I want to know if they had enough space in which to live. The Bible mentions that there were many places they did not obtain. Could the Israelites feed themselves?
According to the Bible, in Exodus 12:37:

And the people of Israel journeyed from Rameses to Succoth, about six hundred thousand men on foot, besides women and children.
Some Scholars believe that the total number of Israelites who left Egypt during the exodus, women and children and old men included, was around 2.4 million people. If we include Egyptians who chose to join the Israelites, the number would be even greater: “Many other people went up with them, and also large droves of livestock, both flocks and herds” (Exodus 12:38).
In the second year after the Israelites left Egypt, Moses took a census of the men in Israel able to fight—all the able-bodied men age twenty and above from all the tribes except the Levites. The number of warriors was 603,550 (Numbers 1:45–46). The Levites were not counted because God commanded Moses to exclude them from the census (verse 49). Instead of going to war, the Levites were to stay and guard the tabernacle (verse 53).
Source: https://www.gotquestions.org/Israelites-exodus.html

With regard to the land that God had promised to his people, the Bible says this in Joshua 1:4:

Your territory will extend from the desert to Lebanon, and from the great river, the Euphrates—all the Hittite country—to the Great Sea on the west.

That area includes all of the land modern Israel currently possesses, plus all of the land of the Palestinians (the West Bank and Gaza), plus some of Egypt and Syria, plus all of Jordan, plus some of Saudi Arabia and Iraq.
Although the Israelites failed to take possession of all the land promised to them, there was more than ample land to accommodate and feed the Israelites.