can I mix. trisodium phosphate, potassium hydroxide, and sodium hydroxide together?
I advise against using potassium or sodium hydroxide in homemade cleaning agents. You could easily end up with a mixture that could severely burn eyes (up to blindness), skin or lungs.

Also, grease from fast food restaurants is fundamentally different from gas station grease. The former consists most probably of fat while the latter is a mineral oil product.

Your home-made degreaser, with a hydroxide concentration that could be handled without complete personal protective equipment, might or might not have some effect on fat due to saponification but for removing mineral oil based grease I would not expect it to be effective.