"J'aime réfléchir avant d'agir."
Translation:I like to think before acting.
Presumably reflechir means "reflect", in the same way English uses it. But while "to reflect before one acts" makes sense, "to think before one acts" is the more common way of expressing that thought in English.
"To think ahead" IMO means to consider the future and maybe make plans for that future. It is not exactly the same thing as "to think before acting".