So adam wasn't the first man?
No, Adam wasn't the first human but he began the Adamic line that led to Christ. In that respect he was the "first man Adam".
There are many differences in the Genesis descriptions of man and Adam. Man(kind) was created on the 6th day,
So God created man in His own image, in the image of God created he him; male and female created he them. (Gen.1:27)
On the seventh day He rested but then ...and there was not a man to till the ground.
And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul. (Gen.2:7)
And the Lord God caused a deep sleep to fall upon Adam, and he slept: and He took one of his ribs, and closed up the flesh instead thereof; And the rib, which the Lord God had taken from man, made He a woman, and brought her unto the man. (Gen.2:21-22)
There were many differences in the two. One was created and one was formed. Mankind was created at the same time as woman. Eve was not formed at the same time. Mankind was given dominion over fish, fowl, etc. while Adam was to till the ground and keep the garden.
My belief is that mankind had an earlier start than the Adamic line. That is why Cain was able to find a wife and start a city when he was banned from the Garden - other people were already there. That is where the different races came from. God created them all but not from one man.