to study; to learn; to gain knowledge or skills

to be like; to be similar to; as if

(of a boat) to sail against the flow; (figuratively) to work hard to make progress in a difficult environment. Often used with 不进则退 bù​jìn​zé​tuì to imply that one must keep moving forward or they will fall behind

to fall back if one does not keep moving forward; progress or perish; if you do not advance, you will regress