A late discovery was made that the Minkowski theory and special relativity theory clearly contradict each other, namely in the treatment of the units of length. Minkowski stretches it indefinitely and SRT cuts it down to zero with a Lorentz factor. Thus, Minkowski's theory is not a description in 4D for the SRT as intended since 1908. It was further investigated which of the two theories should be the correct one and another discovery was made that the speed of light in SRT, if one considers the inversely proportional relativistic length and uses the time unit for this, no longer remains invariant and thus SRT violates its own 2nd postulate, whereby the decision is clear. Subsequently, a modification of the interpretation of the Minkowski theory was proposed to the extent that the relativity principle of the SRT has to be modified and the inertial frames no longer have to be completely rigorously “equal”. They form relativistic levels, which was already given in SRT through time dilation, but was never admitted. Now the length, together with time, is an asymmetrical relativistic property and is subject to a completely identical procedure as the time dilation. There is an equally effective length dilatation and a level relativity was designed and confirmed with other results, which satisfies both postulates. Further relativistic theories provide further arguments. A Gravitational-Doppler-Relativistic explains new discovered impulse and 2nd triplet paradoxes and also makes mass an asymmetrical relativistic attribute. A discovered length “Motirz calculation” reveals the same length measurement error in a direct, very simple and clear way. A new Gravitational Level Relativity GLR is born.