How should one go about achieving a 'decent fundamental understanding' (specific pointers, if you have them). And, how much time must one devote to being a 'go

How should one go about achieving a 'decent fundamental understanding' (specific pointers, if you have them). And, how much time must one devote to being a 'good enough git guru'? (and, it surprises me that gitless is not more popular: https://gitless.com/ https://gitless.com/ )