Hair looks shiny when natural but dull when straightened

Everytime i straighten my hair it ends up looking dull and stiff, ive tried multiple hair products, biosilk, garnier, different hair straighteners and thermal brushes, hair masks, blow drying beforehand, oils, sleeping on satin, small sections, Heat at low and high, Like everything you can think of.

My hair is very thick and wavy and when its in its natural state its super shiny and bouncy but when i straighten it it looks like a big wig and everybody always tells me that it does 😭 . I want to know how to get it sleek and straight I also dont straighten it a lot so its not heat damage It just doesnt come out like everyone elses. It comes out dry and big.