When writing a sequence of actions that happen after each other I get regularly confused about the correct use of the present participle. For example in:
A: I prefer learning by gaining an overview first and then deepen the understanding of the details.
B: I prefer learning by gaining an overview first and then deepening the understanding of the details.
C: I prefer learning by gaining an overview first and by then deepening the understanding of the details.
I’m not sure which grammatical rules should exactly be used here.