How did the so-called Second New Deal differ from the first?Also, what political pressures did Roosevelt face that contributed to the new policies?

I have not come across terms like first and second new deals. However, people do speak of the "Hundred Days" and "Second Hundred Days" two periods of speedy and intensive actions taken under the New Deal Program.

The hundred days refers to the special session of the Congress lasting from March 9, 1933 to June 16, 1933, in which a series of important laws were passed that were intended to provide relief to the needy, give boost to economic activity, and reform financial, business, industrial and agricultural practices.

The second hundred days refers to a period in 1935 when additional laws were passed to further strengthen the achievements flowing from the effects of the original hundred days. The second hundred days did not really differ from the original 100 days. It was actually based on the experience of implementing the original hundred days and built upon it. Accordingly the laws passed during the second hundred days covered many more aspects.

The new deal itself continued well beyond these second hundred days.