The present invention relates to compounds of general formula (I): in which R1, R2, R3, R4, R6, R7, R8, R9, R10, R11, R12, R13 and X are as defined herein, to methods of preparing said compounds, to intermediate compounds useful for preparing said compounds, to pharmaceutical compositions and combinations comprising said compounds and to the use of said compounds for manufacturing a pharmaceutical composition for the treatment or prophylaxis of a disease, in particular of neoplasms, as a sole agent or in combination with other active ingredients.