# pleasing aroma

This refers to the good smell of the roasted meat.

# said in his heart

Here the word "heart" refers to God's thoughts and emotions.

# curse the ground

"do very serious harm to the earth"

# because of mankind

"because mankind is sinful." 

# the intention of mankind's heart is evil from childhood

"from their earliest years they tend to do evil things" or "when they are young, they want to do evil things

# from childhood

"from their youth"