Hi Christina,
Seems the new gear is helping a lot. Great improvement.
Giving advice on BIF I am thumb sucking as you very well know.
With BIF you need to plan ahead and have lots of patience. You should not have any fear of getting dirty either. Planning the shot ahead as to where you want the sun to be and anticipating how the bird will follow a flight path. Getting down to the level of the water avoiding unwanted reflections and predicting carefully what the anticipated dynamic range will be when your subject appears in your viewfinder.
BIF is not a “catch them in the spur of the moment” exercise, it takes lots of planning and patience.
Look at what you have done with this capture. You shot down on a goose with spread out wings busy landing – Wrong! GET DOWN to the water level! Try to get your background far away from your subject so it can be OOF even at F8. With a landing goose you need not use such a high shutter speed.
How many focal points do you have on that D7100. 52? Use them.
I would like to see the shot where the goose hits the water.
You are getting better and better. Keep practising and explore the D7100 and what it can do for you.