How to get my african american type hair to grow long, thick and healthy?

First of all, I love your mix. I think Ethiopians and Somalians are beautiful. Just look at Iman. I understand the frustration of growing hair, I have black, Indian and German blood and so my hair, I think is type 3 curly. The only advice I can offer might be things you've already heard, Eat healthy, don't smoke, limit alcohol and coffee, exercise,etc, those things and of course no harsh chemicals on the hair, try not to relax it or use heat, you use mayo so that's good cos it's natural, extra virgin olive oil is also good;you can get good shampoo's for less, just cos it's expensive doesn't mean it's better. I have recently (for the last year) done all of the above and I can definately notice a difference in my hair. You just have to be patient. Good luck