Hi @Jan Vidlak
If 
and 
, then from the correct free body diagram of the two masses, the sum of forces can be written as follow:
and , then from the correct free body diagram of the two masses, the sum of forces can be written as follow:
,
.Combining the kinematics and these two equations of motion into a single matrix equation yields
From here, you should be able to rewrite the matrix equation into the state-space model with A, B, C, D matrices. In Simulink, you can implement the linear state-space system using the state-space block.
