For flat feet you can a physiotherapist directly as he/she will be able to guide you after assessment about correct insole which helps greatly in flat feet n also exs for your feet muscles and other leg muscle to help you improve..
Navel displacement can be due to some muscular imbalance near your abdominal area which a physiotherapist can help but it can be because of some other systemic problem for that you need a consult from a surgeon or medical specialist
Next Steps
first consult physiotherapist get the feet treatment going along with that she can assess navel displacement n guide you further
Health Tips
wear good sports shoes avoid sneakers for flat chapels .avoid lifting heavy weights till navel displacement is diagnosed correctly