I do gymnastics and I practise things like spits, butterfly kicks and another position where you lie on the floor, lift your chest and head up and then try and get your feet to head without cheating. Becoming flexible will take a long time but if you do it every day then flexibility will increse
if you want more fallibility in your legs, you want to start doing yoga that targets at your legs. I am a figure skater for about 15 yrs. and I have done yoga almost everyday in the summer and it really helps, you just have to keep at it. Depending on how tight you are it depends on how long it will take you do do, lets say a full out slept, or a st rattle stretch. Some stretches help you with hip turn outs which is better for the leg flex ability.
Like Maybe You Can Do The Butterfly . And Maybe Some Toe Touches And Cheerleading Things . A Lot Of Jumps And Things.
Braxton Hicks.