Hi there. An easy exercise that may help (can be done whilst watching television). is to sit on the floor, legs parallel, feet flexed (watch posture here and make sure that you are sitting correctly, arms in second, fingers lightly on the floor). Then simply work the feet to a full point gradually working through the metatarsals.(visualise the shape of a dolphin jumping through the waves - dolphin feet)aim to get the toes to the floor (no mean feet er pardon the pun) Group work with this exercise is fun to do also but MUST be done under supervision of a good teacher and one must not go beyond their limits (SAFE DANCE PRACTICE AND INJURY PREVENTION MUST BE FIRST AND UPMOST IMPORTANCE). get a partner to gently push the feet to the floor and hold for 10 seconds. Remember to keep the backs of the knees on the floor also. Hoping this is of some help at least. Another quick tip to promote foot strength, tendu, tendu and tendu some more (using correct technique of course)
Remember these things do not happen overnight but hopefully in due time, your feet may become more flexible. unfortunately sometimes we cannot change what God has given us so we work to our very best with what we have.