Best thing you can do its lift weights ^^ do squats, lunges, deadlifts and hip thrust.
For cardio you can sprint 2-3 times per week and you will notice big difference in few weeks.
I found running/sprinting made my legs get bigger because of the muscle now I have stopped they seem to be more slender? I find squats, lunges and everyday walking has slimmed my legs down and look more toned ? Maybe it's my body type but running also use to make me have swollen lower leg (hamstring area) x