"You did not respect Matěj."
Translation:Matěje sis nevážila.
I can try. No promises.
Vážit si (reflexive = to respect something or somebody)
nevážit si = obvious negative.
sis = the reflexive version of past. You can also have "jsi si" "Mateje jsi si nevážila" but "sis" is proper Czech as well and faster to say.
Matěje = genitiv of Matěj
There are acceptable variations.
Ty jsi si nevážila Matěje, for example.