curve derivatives

Questions
1

kindly go through excel file. I want to plot this curve with 2 derivatives. one before cooling and one after cooling. I want to use exponential as well as log function for this. Kindly let me know. I tried interpolation but I am not expert so did not get expected results. Thanks

2

Are you using Mathematica? If so, what code do you have so far.

Here is how you import a spreadsheet:

Here is how you fit data to different kinds of models and plot them: