Try not to use gels in your hair, those gradually ruin them and make them curlier than before (I've seen it happen to many naturally straight-haired people).

You can try using argan oil (like Pro Naturals argan oil) or use a keratin straightening system to relax your hair and make it slightly curly instead of IMPOSSIBLY curly.

I've been hearing good things about the Cocoa Keratin System because it lasts for 5 months and comes with shampoo and conditioner. The whole treatment is safe for hair as it's based on Keratin and the shampoo is based on Argan oil which is very beneficial for hair. Hope this helps!