Exponential Interpolation For Different Types Of Curves?

interpolating numbers in excel for an exponential function. I want to know how to be able to curve a curve in 4 different ways essentially the 2 that make up the two halves of a peak and the 2 that make up the two halves of a trough. I've tried using the LINEST function to create this interpolation and it's good to get 1 of the 4 curves I'm interested in. how to do the other 3? I'm also interested in knowing if these functions "whip the tail up" as in almost like how the tail end of a "sin" function flips back up. here it is.

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For this example of the exponential function, it creates the curve in one particular direction. I was wondering how I would do it to have it curve in another direction, for example I was testing the same function, but going downwards, and also having the tail curve back up (by hump I mean to simulate a gaussian distribution with the tails) how would I do that. seems like I now have part 1 of 4 aspects of the curve. here's the attached file to show what I mean. I want to get the hump going up and then sort of reflected along the y-axis and then similar features if I were to reflect the curves on the x axis. is it possible with the functions in excel? Linest test.xlsx