So you reject the concept of the speed of light being constant for all observers? That’s the primary assertion of modern physics. There were demonstrative experiments in time dilation and contraction before Einstein.
You could prove that the speed of light is not constant with a glass tank full of water. (It can also be proven that the acceleration of gravity is not constant either - and that’s something with many practical applications already in use.)
If you’re referring to the relativity assertion, it cannot possibly be true. Two photons headed in opposite directions, put an observer on each. Each observer will be moving away relative to the other at twice the speed of light. Same goes if they started far apart and moved at light speed to a common point. The only way one can pretend otherwise is to ignore the rest of the universe.
You should stop taking faith-based approaches to alleged proofs and seek out alternative, less exotic explanations as a skeptic does... and as a scientist does.