Word by Word Analysis

فَرِيقًا هَدَىٰ وَفَرِيقًا حَقَّ عَلَيْهِمُ ٱلضَّلَـٰلَةُ ۗ إِنَّهُمُ ٱتَّخَذُوا۟ ٱلشَّيَـٰطِينَ أَوْلِيَآءَ مِن دُونِ ٱللَّهِ وَيَحْسَبُونَ أَنَّهُم مُّهْتَدُونَ 30

A group [of you] He guided, and a group deserved [to be in] error. Indeed, they [i.e., the latter] had taken the devils as allies instead of Allāh while they thought that they were guided.